Advanced High School Chemistry Flashcards: Complete 9-Part Course Review
Review a rigorous nine-part high school chemistry course with 450 concise cards covering concepts, models, equations, calculation setup, and lab reasoning.
Sobre este mazo
Study advanced high school chemistry through 450 independently written English flashcards arranged as one nine-part sequence. The course moves from atomic structure and bonding to properties of substances and mixtures, reactions, kinetics, thermochemistry, equilibrium, acids and bases, thermodynamics, and electrochemistry. Prerequisites appear before dependent models and calculations.
What the cards practice
The cards practice five useful recall paths: concept to explanation; model or representation to interpretation; equation to meaning and use; short setup to a result with units and reasoning; and laboratory observation to a chemical conclusion. This includes definitions, relationships, conditions, contrasts, particle and energy models, focused calculation steps, measurements, errors, and visible changes.
Selected reverse and contrast prompts appear only when the reverse direction has one clear standalone target. Mechanical permutations, graph-dependent prompts that need a missing figure, copied test formats, long multipart derivations, and visual recall tied to third-party figures are excluded. The review scheduler handles long-term spacing after installation.
The prompts, answers, examples, organization, metadata, and cover were created independently from common chemistry knowledge and original work. No protected questions, answer choices, scoring materials, curriculum prose, commercial card text, source figures, or third-party media were copied.
The Common knowledge · CC0 1.0 label applies only to the original prompts, answers, examples, organization, metadata, and cover, to the extent applicable rights exist. It does not claim ownership of scientific facts, equations, or third-party material.
Tarjetas de este mazo
Tarjeta 1
Pregunta
What does one mole count?
Respuesta
Exactly 6.02214076 × 10^23 representative particles.
Tarjeta 2
Pregunta
What does a peak in an element's mass spectrum represent?
Respuesta
An isotope with a particular mass-to-charge ratio; for singly charged monatomic ions, the position tracks isotopic mass.
Tarjeta 3
Pregunta
What does an empirical formula show?
Respuesta
The lowest whole-number ratio of the elements' atoms in a compound.
Tarjeta 4
Pregunta
How does a mixture differ from a pure substance at the particle level?
Respuesta
A mixture contains chemically distinct representative units in variable proportions; a pure substance contains one element or compound with fixed composition. Different isotopes do not make an elemental sample a mixture.
Tarjeta 5
Pregunta
Which particles make up an atom's nucleus?
Respuesta
Protons and neutrons. Electrons occupy the space outside the nucleus.
Tarjeta 6
Pregunta
What does a larger binding energy on a PES spectrum mean?
Respuesta
More energy is required to remove that electron, so it is held more strongly by the nucleus.
Tarjeta 7
Pregunta
How does atomic radius generally change across a period and down a group?
Respuesta
It decreases from left to right as effective nuclear charge rises, and it increases down a group as additional electron shells increase distance and shielding.
Tarjeta 8
Pregunta
What typical ion charge do Group 1 metals form?
Respuesta
+1, by losing their one valence electron.
Tarjeta 9
Pregunta
How do you convert moles to particles?
Respuesta
Multiply by Avogadro's number: particles = moles × 6.022 × 10^23 mol^-1.
Tarjeta 10
Pregunta
How is average atomic mass estimated from isotope data?
Respuesta
Add each isotopic mass multiplied by its fractional abundance.
Tarjeta 11
Pregunta
How is an element's mass percent in a compound calculated?
Respuesta
Divide the mass contributed by that element by the compound's molar mass, then multiply by 100%.
Tarjeta 12
Pregunta
How can measured elemental composition reveal a sample's purity?
Respuesta
Compare the measured mass fraction with the fraction expected for the pure compound; a mismatch indicates another component.
Tarjeta 13
Pregunta
How do you build a ground-state electron configuration with the Aufbau principle?
Respuesta
For ordinary ground states, move through the periodic table in atomic-number order, filling each s, p, d, or f block as it appears. The subshell capacities are s², p⁶, d¹⁰, and f¹⁴. For example, Br is [Ar] 4s² 3d¹⁰ 4p⁵.
Tarjeta 14
Pregunta
What does the relative area or height of an ideal PES peak indicate?
Respuesta
The relative number of electrons in the corresponding subshell.
Tarjeta 15
Pregunta
How does first ionization energy generally change across a period and down a group?
Respuesta
It increases from left to right as effective nuclear charge rises, and it decreases down a group as distance and shielding make a valence electron easier to remove.
Tarjeta 16
Pregunta
Why do elements in the same group form similar compounds?
Respuesta
Their ground-state valence patterns repeat, including which outer subshells are full or partly full. That leads to similar bonding and typical ion charges.
Tarjeta 17
Pregunta
How do you convert a sample's mass to moles?
Respuesta
Divide its mass by its molar mass: n = m/M.
Tarjeta 18
Pregunta
Which mass-spectrum interpretation lies outside the usual single-element model used in this deck?
Respuesta
Assigning peaks in mixtures or peaks from multiply charged or polyatomic species; the standard model uses singly charged monatomic ions of one element.
Tarjeta 19
Pregunta
What does the law of definite proportions state?
Respuesta
Every pure sample of a given compound has the same element mass ratios.
Tarjeta 20
Pregunta
Why can two samples of the same mixture have different compositions?
Respuesta
Mixture components are physically combined, so their relative amounts are not fixed by a chemical formula.
Tarjeta 21
Pregunta
How does Coulomb's law connect charge and separation to attraction?
Respuesta
Attraction grows with the magnitude of the charge product and decreases with the square of the separation distance.
Tarjeta 22
Pregunta
Which PES electrons usually appear at the highest binding energy?
Respuesta
Core electrons closest to the nucleus, because they feel the strongest nuclear attraction.
Tarjeta 23
Pregunta
How does electron affinity generally change across a period and down a group?
Respuesta
Electron gain generally becomes more favorable from left to right across a period and less favorable down a group as distance and shielding increase. Stable subshell patterns create substantial exceptions.
Tarjeta 24
Pregunta
Why are alkali metals generally more reactive down the group?
Respuesta
Their valence electron is farther from the nucleus and easier to remove.
Tarjeta 25
Pregunta
How many moles are in 18.0 g of H₂O?
Respuesta
About 0.999 mol. Use 18.0 g ÷ 18.02 g mol^-1.
Tarjeta 26
Pregunta
An element is 75% isotope 10 and 25% isotope 11; what is its average atomic mass?
Respuesta
10.25 u. Calculate (0.75 × 10) + (0.25 × 11).
Tarjeta 27
Pregunta
A compound is 40.0% C, 6.7% H, and 53.3% O by mass; what is its empirical formula?
Respuesta
CH₂O. For a 100 g sample, convert each mass to moles and divide by the smallest amount.
Tarjeta 28
Pregunta
A 10.0 g impure sample contains 8.5 g of the target compound; what is its mass-percent purity?
Respuesta
85%. Calculate (8.5 g ÷ 10.0 g) × 100%.
Tarjeta 29
Pregunta
Which electrons are removed first when a transition metal forms a cation?
Respuesta
Electrons in the occupied orbital with the highest principal quantum number: 4s before 3d. For example, Fe²⁺ is [Ar] 3d⁶.
Tarjeta 30
Pregunta
A PES spectrum has peaks proportional to 2, 2, and 6 electrons; which configuration fits?
Respuesta
1s² 2s² 2p⁶, the configuration of Ne.
Tarjeta 31
Pregunta
How does electronegativity generally change across a period and down a group?
Respuesta
It increases from left to right across a period and decreases down a group as atomic size and shielding increase.
Tarjeta 32
Pregunta
What empirical formula results from Al³⁺ and O²⁻?
Respuesta
Al₂O₃, because two Al³⁺ ions balance three O²⁻ ions.
Tarjeta 33
Pregunta
How does a particle's mass in atomic mass units relate to its molar mass?
Respuesta
The numerical value is the same: a molecular or formula-unit mass of x u corresponds to a molar mass of x g mol^-1.
Tarjeta 34
Pregunta
What does the tallest isotope peak usually indicate in a simple mass spectrum?
Respuesta
The most abundant isotope, assuming comparable detection response and singly charged ions.
Tarjeta 35
Pregunta
How much oxygen is present in 25.0 g of a compound that is 32.0% oxygen by mass?
Respuesta
8.00 g O. Multiply 25.0 g by 0.320.
Tarjeta 36
Pregunta
What does a particle diagram with two unbonded species in changing ratios represent?
Respuesta
A mixture, because more than one particle type is present and the ratio is not fixed in a formula unit.
Tarjeta 37
Pregunta
What distinguishes valence electrons from core electrons?
Respuesta
Valence electrons are available for bonding or ion formation; main-group valence electrons occupy the outermost shell, while transition metals may also use (n−1)d electrons. Core electrons mainly shield nuclear charge.
Tarjeta 38
Pregunta
Why can PES peak groups reveal an atom's occupied subshells?
Respuesta
Electrons in different subshells require distinct removal energies, producing separate binding-energy groups.
Tarjeta 39
Pregunta
How do ion radii compare with neutral atoms and within an isoelectronic series?
Respuesta
Cations are smaller than their neutral atoms, while anions are larger. Among species with the same electron count, more protons pull the electrons closer and produce the smaller radius.
Tarjeta 40
Pregunta
What formula is expected for a compound between a Group 2 metal M and a Group 17 nonmetal X?
Respuesta
MX₂, because M forms M²⁺ and X forms X⁻.
Tarjeta 41
Pregunta
When is a covalent bond considered nonpolar?
Respuesta
When the bonded atoms have identical or very similar electronegativities, so the shared electron density is distributed approximately evenly.
Tarjeta 42
Pregunta
Why does a bonded pair of atoms have an equilibrium bond length?
Respuesta
At that separation, attractive and repulsive interactions balance at minimum potential energy.
Tarjeta 43
Pregunta
How are particles arranged in an ionic solid?
Respuesta
Cations and anions occupy a repeating three-dimensional lattice held by electrostatic attraction.
Tarjeta 44
Pregunta
What model explains bonding in a metal?
Respuesta
Positive metal cores are held together by attraction to mobile, delocalized valence electrons.
Tarjeta 45
Pregunta
How do you construct a Lewis diagram?
Respuesta
Count total valence electrons, adding electrons for a negative charge and subtracting them for a positive charge. Choose a skeleton, connect atoms with single bonds, complete terminal duets or octets, and place remaining electrons on the central atom. Add multiple bonds if needed, then check the electron total and formal charges.
Tarjeta 46
Pregunta
What does resonance mean in a molecule or ion?
Respuesta
Resonance uses two or more valid Lewis diagrams with the same atom arrangement but different electron placement. The actual electron distribution is a hybrid; equivalent contributors have equal weight.
Tarjeta 47
Pregunta
What determines molecular shape in VSEPR theory?
Respuesta
Electron domains around the central atom arrange to minimize repulsions.
Tarjeta 48
Pregunta
How does an ionic bond differ from a covalent bond?
Respuesta
Ionic bonding is attraction among oppositely charged ions in an extended structure; covalent bonding uses shared electron density between atoms.
Tarjeta 49
Pregunta
What happens to potential energy when bonded atoms are pushed much closer than equilibrium?
Respuesta
Potential energy rises sharply because nucleus–nucleus and electron–electron repulsions dominate.
Tarjeta 50
Pregunta
Why are many ionic solids brittle?
Respuesta
A shifted lattice can align like charges, creating strong repulsion that splits the crystal.
Tarjeta 51
Pregunta
What molecular shapes arise from two electron domains with no lone pairs and from three domains with zero or one lone pair?
Respuesta
Two bonding domains give linear with a 180° angle. Three domains with no lone pairs give trigonal planar with 120° angles; replacing one bond with a lone pair gives bent with an angle slightly below 120°.
Tarjeta 52
Pregunta
Why are metals electrically conductive as solids?
Respuesta
Their delocalized electrons can move through the solid when an electric field is applied.
Tarjeta 53
Pregunta
How is formal charge calculated for an atom in a Lewis diagram?
Respuesta
Formal charge = valence electrons − nonbonding electrons − half the bonding electrons.
Tarjeta 54
Pregunta
Why can't electronegativity difference alone classify a bond as ionic or covalent?
Respuesta
Bonding lies on a continuum. A larger difference means more ionic character, but the element types and especially the compound's properties give the best classification.
Tarjeta 55
Pregunta
Which shapes and bond-angle trends arise as lone pairs replace bonds in four electron domains?
Respuesta
Four bonds give tetrahedral with ideal 109.5° angles. One lone pair gives trigonal pyramidal with smaller angles; two lone pairs give bent with typically smaller angles again because lone pairs repel more strongly than bonding pairs.
Tarjeta 56
Pregunta
What feature of a potential-energy curve represents bond dissociation energy?
Respuesta
The energy difference from the curve's minimum to the separated-atoms limit.
Tarjeta 57
Pregunta
When does an ionic compound conduct electricity?
Respuesta
When molten or dissolved so its ions can move; not as a rigid solid lattice.
Tarjeta 58
Pregunta
What is a substitutional alloy?
Respuesta
An alloy in which atoms of a similar size replace some host-metal atoms in the lattice.
Tarjeta 59
Pregunta
How do two, three, and four electron domains map to hybridization?
Respuesta
Two domains map to sp, three to sp², and four to sp³, with ideal angles of 180°, 120°, and 109.5°. Hybridization involving d orbitals is outside this deck’s scope.
Tarjeta 60
Pregunta
What usually makes one resonance contributor more favorable than another?
Respuesta
Smaller formal-charge magnitudes, appropriate negative charge on more electronegative atoms, and complete valence shells where applicable.
Tarjeta 61
Pregunta
How many sigma and pi bonds are in single, double, and triple bonds?
Respuesta
A single bond has one sigma bond; a double has one sigma and one pi bond; a triple has one sigma and two pi bonds. Head-on sigma overlap is stronger than side-by-side pi overlap.
Tarjeta 62
Pregunta
Why is a polar covalent bond polar?
Respuesta
Unequal electronegativity creates an uneven sharing of electron density and partial charges.
Tarjeta 63
Pregunta
Which molecular shapes arise as lone pairs replace bonds in five electron domains?
Respuesta
Five bonds give trigonal bipyramidal; four bonds and one lone pair give seesaw; three bonds and two lone pairs give T-shaped; two bonds and three lone pairs give linear.
Tarjeta 64
Pregunta
How do ionic charge and ionic radius affect attraction between ions?
Respuesta
Larger charge magnitudes and smaller ionic radii produce stronger attraction because the charge product increases and the ion centers are closer.
Tarjeta 65
Pregunta
Why do ionic solids often have high melting points?
Respuesta
Many strong Coulombic attractions throughout the lattice must be overcome to free the ions.
Tarjeta 66
Pregunta
What is an interstitial alloy?
Respuesta
A smaller atom occupies holes between host-metal atoms, often making lattice layers harder to slide.
Tarjeta 67
Pregunta
What shape has six bonding domains and no lone pairs on the central atom?
Respuesta
Octahedral.
Tarjeta 68
Pregunta
Which elements commonly form incomplete octets in stable Lewis diagrams?
Respuesta
Hydrogen forms a duet, and electron-deficient central atoms such as boron or beryllium can have fewer than eight electrons.
Tarjeta 69
Pregunta
How do bond order and atomic size affect covalent bond length and strength?
Respuesta
Within a comparable bond family, higher bond order gives shorter, stronger bonds. Larger bonded atoms generally give longer bonds, which are often weaker because their orbitals overlap less effectively.
Tarjeta 70
Pregunta
What bonding model best fits a sample that is malleable and conducts as a solid?
Respuesta
Metallic bonding with mobile, delocalized electrons and nondirectional attractions.
Tarjeta 71
Pregunta
What shape has six electron domains, five bonds, and one lone pair?
Respuesta
Square pyramidal.
Tarjeta 72
Pregunta
Which lattice should have stronger attractions: MgO or NaCl, assuming similar separations?
Respuesta
MgO, because the charge product for Mg²⁺ and O²⁻ is larger than for Na⁺ and Cl⁻.
Tarjeta 73
Pregunta
Why are pure metals often malleable?
Respuesta
Metal cores can shift while the mobile electron sea maintains nondirectional attraction instead of exposing fixed like-charge planes.
Tarjeta 74
Pregunta
What is the best Lewis structure for CO₂?
Respuesta
O=C=O, with two lone pairs on each oxygen and no formal charges.
Tarjeta 75
Pregunta
What shape has six electron domains, four bonds, and two opposite lone pairs?
Respuesta
Square planar.
Tarjeta 76
Pregunta
What limitation does an odd total number of valence electrons create for a Lewis diagram?
Respuesta
At least one electron must remain unpaired, so not every atom can have a complete paired-electron octet.
Tarjeta 77
Pregunta
What does a higher bond order do to a bond's potential-energy curve?
Respuesta
It generally places the minimum at a shorter internuclear distance and makes the well deeper, corresponding to a shorter bond and a larger bond-dissociation energy.
Tarjeta 78
Pregunta
When can a carbon–carbon double bond produce geometric isomers?
Respuesta
When each carbon has two different substituents. The pi bond restricts rotation, so distinct spatial arrangements can persist.
Tarjeta 79
Pregunta
When may a third-period central atom exceed an octet in a Lewis diagram?
Respuesta
When the valid electron count and lower formal charges favor an expanded valence shell, as in species such as SF₆.
Tarjeta 80
Pregunta
How do you decide whether a molecule with polar bonds is polar overall?
Respuesta
Add the bond-dipole vectors using the molecular shape; symmetry may cancel them, while an asymmetric arrangement leaves a net dipole.
Tarjeta 81
Pregunta
Which interparticle forces act between all atoms and molecules?
Respuesta
London dispersion forces, caused by temporary and induced dipoles.
Tarjeta 82
Pregunta
What four broad solid types does this deck compare?
Respuesta
Ionic, metallic, molecular, and covalent-network solids.
Tarjeta 83
Pregunta
How do gas particles differ from liquid particles?
Respuesta
Gas particles are much farther apart and move independently; liquid particles stay close but can move past one another.
Tarjeta 84
Pregunta
What relationship connects pressure, volume, amount, and temperature for an ideal gas?
Respuesta
PV = nRT, with absolute temperature in kelvins and units consistent with R.
Tarjeta 85
Pregunta
What does temperature measure in kinetic molecular theory?
Respuesta
The particles' average translational kinetic energy.
Tarjeta 86
Pregunta
What two ideal-gas assumptions fail most clearly for real gases?
Respuesta
Particles have nonzero volume and experience intermolecular attractions.
Tarjeta 87
Pregunta
How is molarity defined?
Respuesta
Moles of solute per liter of solution: M = n/V.
Tarjeta 88
Pregunta
What must a correct particulate diagram of NaCl(aq) show?
Respuesta
Separated Na⁺ and Cl⁻ ions in a 1:1 ratio, each surrounded by oriented water molecules.
Tarjeta 89
Pregunta
Which separation method removes an insoluble solid from a liquid?
Respuesta
Filtration: the solid stays as residue while the liquid passes as filtrate.
Tarjeta 90
Pregunta
What does “like dissolves like” mean at the particle level?
Respuesta
A solute tends to dissolve when new solute–solvent attractions can compete with the attractions disrupted in the pure substances.
Tarjeta 91
Pregunta
What happens when matter absorbs electromagnetic radiation?
Respuesta
Its particles move to an allowed higher-energy state when the photon energy matches the energy gap.
Tarjeta 92
Pregunta
Which equations connect photon energy, frequency, and wavelength?
Respuesta
E = hν and c = λν.
Tarjeta 93
Pregunta
What is the Beer–Lambert law?
Respuesta
A = εbc: absorbance equals molar absorptivity at the chosen wavelength times path length times concentration.
Tarjeta 94
Pregunta
What molecular features generally strengthen London dispersion forces?
Respuesta
More electrons and a more polarizable cloud strengthen temporary dipoles; greater contact area and accessible π-electron density can also strengthen the attraction.
Tarjeta 95
Pregunta
Why do molecular solids usually have low melting points and fail to conduct electricity?
Respuesta
Distinct molecules are held together by relatively weak intermolecular forces, while their valence electrons stay localized in bonds and lone pairs.
Tarjeta 96
Pregunta
How do particles move in a solid?
Respuesta
They vibrate about fixed positions and do not translate past one another.
Tarjeta 97
Pregunta
What graph shapes connect V or P with T(K) or n for an ideal gas?
Respuesta
All four are straight lines through the origin: V versus T(K) at fixed n and P; P versus T(K) at fixed n and V; V versus n at fixed P and T; and P versus n at fixed V and T.
Tarjeta 98
Pregunta
At the same temperature, which gas has the greater average molecular speed: He or Xe?
Respuesta
He. Both have the same average kinetic energy, but KE = ½mv² means the lower-mass particles move faster.
Tarjeta 99
Pregunta
Why do real gases deviate more at high pressure?
Respuesta
Particles are crowded, so their own volume is no longer negligible compared with the container volume.
Tarjeta 100
Pregunta
Which relationship describes dilution when solute amount is conserved?
Respuesta
M₁V₁ = M₂V₂.
Tarjeta 101
Pregunta
Why does an aqueous ionic solution conduct electricity?
Respuesta
Dissolved ions are mobile and carry charge through the solution.
Tarjeta 102
Pregunta
Which property lets simple distillation separate two liquids?
Respuesta
A sufficient difference in volatility or boiling point, so the vapor is enriched in the more volatile component.
Tarjeta 103
Pregunta
Why are many ionic compounds soluble in water but poorly soluble in a nonpolar solvent?
Respuesta
Water can form strong ion–dipole attractions that stabilize separated ions; a nonpolar solvent cannot provide comparable attractions.
Tarjeta 104
Pregunta
Which molecular transition is commonly associated with microwave absorption?
Respuesta
A transition between quantized rotational energy levels.
Tarjeta 105
Pregunta
What frequency corresponds to a 600. nm photon?
Respuesta
5.00 × 10^14 s^-1. Use ν = c/λ with 600. nm = 6.00 × 10^-7 m.
Tarjeta 106
Pregunta
What is the absorbance to two significant figures when ε = 2.0 × 10² L mol^-1 cm^-1, b = 1.00 cm, and c = 0.0020 M?
Respuesta
0.40. Use A = εbc.
Tarjeta 107
Pregunta
What conditions allow hydrogen bonding between two molecules?
Respuesta
One molecule must donate an H covalently bonded to N, O, or F, and the other must provide a lone pair on N, O, or F. A molecule can be a donor, an acceptor, or both.
Tarjeta 108
Pregunta
Why are covalent-network solids often very hard with high melting points?
Respuesta
A continuous network of strong covalent bonds must be disrupted to deform or melt the solid.
Tarjeta 109
Pregunta
Why do a substance's solid and liquid phases usually have similar molar volumes?
Respuesta
Their particles remain in close contact in both phases, even though liquid particles can move past one another.
Tarjeta 110
Pregunta
How is a gas mixture's total pressure related to its component pressures?
Respuesta
Ptotal = ΣPi; each partial pressure is the pressure that component would exert alone in the same volume and temperature.
Tarjeta 111
Pregunta
What microscopic events create gas pressure?
Respuesta
Gas particles collide with container walls and transfer momentum.
Tarjeta 112
Pregunta
Why do intermolecular attractions matter more for gases at low temperature?
Respuesta
Particles move more slowly, so attractions can alter their paths and promote condensation.
Tarjeta 113
Pregunta
What is the final concentration after 50.0 mL of 2.00 M solution is diluted to 200.0 mL?
Respuesta
0.500 M. Use M₂ = M₁V₁/V₂.
Tarjeta 114
Pregunta
What must a particulate representation of a solution communicate?
Respuesta
The relative concentrations of its components and the particle-level interactions among those components.
Tarjeta 115
Pregunta
What causes components to separate in chromatography?
Respuesta
They differ in attraction to the stationary phase and the mobile phase, so they travel at different rates.
Tarjeta 116
Pregunta
Why are many polar molecular solutes soluble in water?
Respuesta
Dipole attractions or hydrogen bonds with water can replace the solute–solute and water–water attractions disrupted during mixing.
Tarjeta 117
Pregunta
Why does an atom produce discrete spectral lines?
Respuesta
Its electrons can occupy only quantized energy levels, so only photons matching allowed energy differences are absorbed or emitted.
Tarjeta 118
Pregunta
How does photon energy change when frequency doubles?
Respuesta
It doubles because E = hν.
Tarjeta 119
Pregunta
Why is a calibration curve useful in spectrophotometry?
Respuesta
It relates measured absorbance to known concentrations, letting an unknown concentration be read by interpolation within the linear range.
Tarjeta 120
Pregunta
How does an ion–dipole attraction form, and how does it compare with dipole–dipole attraction?
Respuesta
An ion attracts the oppositely charged end of a polar molecule. Ion–dipole attractions tend to be stronger than dipole–dipole attractions.
Tarjeta 121
Pregunta
Which solid type is usually both conductive and malleable?
Respuesta
A metallic solid, because its delocalized electrons move and its nondirectional bonding tolerates layer shifts.
Tarjeta 122
Pregunta
How does a crystalline solid differ from an amorphous solid?
Respuesta
A crystalline solid has long-range repeating order; an amorphous solid lacks that long-range periodic arrangement.
Tarjeta 123
Pregunta
How is a gas component's partial pressure found from mole fraction?
Respuesta
Pi = XiPtotal.
Tarjeta 124
Pregunta
How does heating a fixed-volume gas affect its pressure in the ideal model?
Respuesta
Pressure rises because faster particles collide with the walls more forcefully and frequently.
Tarjeta 125
Pregunta
Why can attractions make a real gas's measured pressure lower than the ideal prediction?
Respuesta
Attractions pull approaching particles away from the walls, reducing momentum transfer during wall collisions.
Tarjeta 126
Pregunta
How many moles of ions result from complete dissolution of 0.20 mol CaCl₂?
Respuesta
0.60 mol ions: 0.20 mol Ca²⁺ plus 0.40 mol Cl⁻.
Tarjeta 127
Pregunta
How should water orient around Cl⁻ in a particle model?
Respuesta
Its partially positive hydrogen ends point toward Cl⁻.
Tarjeta 128
Pregunta
Can filtration separate dissolved components of a liquid solution?
Respuesta
No. Dissolved particles pass through the filter with the solvent; filtration only retains an insoluble solid.
Tarjeta 129
Pregunta
Why do nonpolar molecular solutes often dissolve in nonpolar solvents?
Respuesta
Both rely mainly on compatible London dispersion forces, so mixing can replace the attractions disrupted in the separate substances.
Tarjeta 130
Pregunta
What does a shorter absorbed wavelength imply about an energy transition?
Respuesta
A larger energy gap because E = hc/λ.
Tarjeta 131
Pregunta
What is the energy of a photon with frequency 5.0 × 10^14 s^-1?
Respuesta
3.3 × 10^-19 J. Multiply by Planck's constant: E = (6.626 × 10^-34 J·s)(5.0 × 10^14 s^-1).
Tarjeta 132
Pregunta
How does doubling cuvette path length affect absorbance in the linear Beer–Lambert range?
Respuesta
Absorbance doubles if concentration and molar absorptivity stay constant.
Tarjeta 133
Pregunta
How can noncovalent interactions affect a large biomolecule?
Respuesta
Attractions between molecules or between different regions of the same molecule help set its shape, which strongly affects its properties and function.
Tarjeta 134
Pregunta
Why does an ionic solid usually fail to conduct as a solid?
Respuesta
Its ions are fixed in lattice positions. The same substance conducts when molten or dissolved because the ions can then move.
Tarjeta 135
Pregunta
Why does a gas have no definite shape or volume?
Respuesta
Its widely spaced particles move constantly and experience minimal interparticle attraction, so they spread through the available container.
Tarjeta 136
Pregunta
What graph shapes show the inverse pressure–volume relationship for a fixed amount of ideal gas at constant temperature?
Respuesta
A plot of P against V is a decreasing curve, while P against 1/V is a straight line through the origin.
Tarjeta 137
Pregunta
At the same temperature, do different ideal gases have different average kinetic energies?
Respuesta
No. Average translational kinetic energy depends only on absolute temperature.
Tarjeta 138
Pregunta
Under which conditions is ideal-gas behavior most accurate?
Respuesta
Low pressure and high temperature, where particles are far apart and attractions matter least.
Tarjeta 139
Pregunta
What particle-level feature distinguishes a solution from a heterogeneous mixture?
Respuesta
A solution—whether solid, liquid, or gas—is uniform throughout; a heterogeneous mixture has regions or phases with different compositions.
Tarjeta 140
Pregunta
How should water orient around Na⁺ in a particulate model?
Respuesta
Its partially negative oxygen end points toward Na⁺.
Tarjeta 141
Pregunta
In paper chromatography, why does one solute spot travel farther than another?
Respuesta
It interacts more strongly with the mobile phase or more weakly with the stationary phase. With known phase polarities, that travel difference can reveal relative solute polarity.
Tarjeta 142
Pregunta
What energy competition helps explain whether an ionic solid dissolves?
Respuesta
The energy needed to separate lattice ions competes with the energy released when ion–solvent attractions form.
Tarjeta 143
Pregunta
Which molecular motions commonly absorb infrared radiation?
Respuesta
Bond vibrations whose changing dipole can interact with the radiation.
Tarjeta 144
Pregunta
Why must wavelength be converted to meters in c = λν when c is in m s^-1?
Respuesta
Consistent units are required so meters cancel correctly and frequency comes out in s^-1.
Tarjeta 145
Pregunta
How can fingerprints on a cuvette affect a visible-light absorbance reading?
Respuesta
They can absorb or scatter extra light, making measured absorbance too high and the inferred concentration too high.
Tarjeta 146
Pregunta
What causes and controls the strength of dipole–dipole attractions?
Respuesta
Opposite partial charges on neighboring polar molecules attract. Strength increases with larger molecular dipoles and depends on how favorably the dipoles are oriented.
Tarjeta 147
Pregunta
Why is graphite conductive and soft while diamond is insulating and hard?
Respuesta
Graphite has delocalized electrons within its sheets, so it conducts, and its layers can slide, so it is soft. Diamond has a rigid three-dimensional network of localized covalent bonds, making it hard and insulating.
Tarjeta 148
Pregunta
Why are gases much more compressible than liquids?
Respuesta
Gas particles have large empty spaces between them; liquid particles are already close together.
Tarjeta 149
Pregunta
What volume does 0.500 mol CO₂ occupy at 1.00 atm and 300. K if it behaves ideally?
Respuesta
12.3 L. Use V = nRT/P = (0.500 mol)(0.08206 L atm mol^-1 K^-1)(300. K)/(1.00 atm).
Tarjeta 150
Pregunta
Why does a lighter gas effuse faster than a heavier gas at the same temperature?
Respuesta
Its particles have a higher average speed because equal average kinetic energy is shared by less mass.
Tarjeta 151
Pregunta
How does finite particle volume affect a real gas at very high pressure?
Respuesta
The free volume available for particle motion is smaller than the container volume assumed by the ideal model.
Tarjeta 152
Pregunta
How should 250.0 mL of 0.100 M NaCl be prepared from solid NaCl?
Respuesta
Dissolve 0.0250 mol NaCl, or 1.46 g, then dilute to exactly 250.0 mL in a volumetric flask.
Tarjeta 153
Pregunta
What changes in a particle diagram when a solution is diluted without losing solute?
Respuesta
The solute-particle count stays constant while solvent volume and particle spacing increase.
Tarjeta 154
Pregunta
Why is fractional distillation better than simple distillation for liquids with close boiling points?
Respuesta
Repeated vaporization–condensation steps enrich the vapor in the more volatile component more effectively.
Tarjeta 155
Pregunta
Why are oil and water usually immiscible?
Respuesta
Water's strong hydrogen-bond network isn't replaced by equally strong water–oil attractions, so the substances separate into phases.
Tarjeta 156
Pregunta
Which molecular transition is commonly associated with ultraviolet or visible absorption?
Respuesta
A transition between electronic energy levels.
Tarjeta 157
Pregunta
Which photon carries more energy, blue light or red light?
Respuesta
Blue light, because it has shorter wavelength and higher frequency.
Tarjeta 158
Pregunta
Why is absorbance often measured at the wavelength of maximum absorbance in Beer–Lambert analysis?
Respuesta
It gives the largest concentration-sensitive signal, and the flat top near the maximum makes small wavelength-setting errors less influential.
Tarjeta 159
Pregunta
What creates a dipole–induced-dipole attraction, and what controls its strength?
Respuesta
A permanent dipole distorts a nearby nonpolar particle's electron cloud and creates an attractive temporary dipole. A larger permanent dipole and a more polarizable nonpolar partner make the attraction stronger.
Tarjeta 160
Pregunta
How do stronger intermolecular forces affect vapor pressure, boiling point, and melting point?
Respuesta
They lower vapor pressure and raise boiling point. Melting point often rises too, but the trend is less direct because melting rearranges rather than fully separates particles.
Tarjeta 161
Pregunta
How do particles behave in a liquid?
Respuesta
They stay in close contact while moving and colliding continuously. Temperature and interparticle attractions affect their arrangement and motion.
Tarjeta 162
Pregunta
Why must Celsius temperature be converted to kelvins in gas-law calculations?
Respuesta
Gas-law proportionalities require an absolute temperature scale whose zero corresponds to zero extrapolated thermal motion.
Tarjeta 163
Pregunta
How does raising temperature change a Maxwell–Boltzmann speed distribution?
Respuesta
The distribution broadens, its peak lowers and shifts right, and a larger fraction of particles have high speed.
Tarjeta 164
Pregunta
Why does the ideal-gas model treat collisions as elastic?
Respuesta
It assumes total kinetic energy is conserved in particle–particle and particle–wall collisions.
Tarjeta 165
Pregunta
How many moles of solute are in 75.0 mL of a 0.400 M solution?
Respuesta
0.0300 mol. Multiply 0.400 mol L^-1 by 0.0750 L.
Tarjeta 166
Pregunta
For equal solution volumes drawn at the same scale, what shows which solution is more concentrated?
Respuesta
The more concentrated diagram contains more solute particles in that equal volume.
Tarjeta 167
Pregunta
How do differences in intermolecular attractions let distillation separate a liquid solution?
Respuesta
They give the components different vapor pressures, so the vapor is enriched in the more volatile component.
Tarjeta 168
Pregunta
What comparison helps predict whether two liquids will be miscible?
Respuesta
Liquids with similar types and strengths of intermolecular attractions are more likely to mix uniformly.
Tarjeta 169
Pregunta
How can an absorption spectrum help identify a substance?
Respuesta
Its allowed energy gaps produce a characteristic pattern of absorbed wavelengths that can be compared with known spectra.
Tarjeta 170
Pregunta
How does absorbing or emitting a photon change an atom's or molecule's energy?
Respuesta
Absorption raises the species' energy by exactly the photon energy; emission lowers it by the same amount.
Tarjeta 171
Pregunta
What macroscopic evidence can support that a chemical reaction occurred?
Respuesta
Evidence can include gas formation, precipitate formation, a persistent color change, or an energy change, interpreted with particle-level changes.
Tarjeta 172
Pregunta
What does a net ionic equation include?
Respuesta
Only the dissolved or reacting species that undergo chemical change; spectator ions are omitted.
Tarjeta 173
Pregunta
What must a correct particulate reaction diagram conserve?
Respuesta
The number of atoms of every element and the total charge.
Tarjeta 174
Pregunta
What distinguishes a chemical change from a physical change?
Respuesta
A chemical change rearranges bonds into new substances; a physical change alters state or arrangement without changing chemical identity.
Tarjeta 175
Pregunta
What does a balanced equation's coefficient ratio provide?
Respuesta
The mole ratio among reacting and produced species.
Tarjeta 176
Pregunta
What is the equivalence point of a titration?
Respuesta
The point where titrant and analyte have reacted in the stoichiometric ratio given by the balanced equation.
Tarjeta 177
Pregunta
What defines a precipitation reaction?
Respuesta
Aqueous ions combine to form a sparingly soluble solid.
Tarjeta 178
Pregunta
What happens in a Brønsted–Lowry acid–base reaction?
Respuesta
A proton transfers from the acid (donor) to the base (acceptor). In aqueous solution, H₂O can play either role.
Tarjeta 179
Pregunta
What does oxidation mean in a redox reaction?
Respuesta
Loss of electrons and an increase in oxidation number.
Tarjeta 180
Pregunta
What particle-level change confirms that a process is chemical?
Respuesta
Atoms rearrange into new combinations, producing substances with different compositions.
Tarjeta 181
Pregunta
Which ions are spectators when AgNO₃(aq) reacts with NaCl(aq)?
Respuesta
Na⁺ and NO₃⁻. The net ionic reaction is Ag⁺(aq) + Cl⁻(aq) → AgCl(s).
Tarjeta 182
Pregunta
How does a particulate diagram reveal the limiting reactant?
Respuesta
After forming the maximum product allowed by the ratio, none of the limiting reactant remains while excess reactant particles do.
Tarjeta 183
Pregunta
Is melting ice a chemical or physical change?
Respuesta
A physical change. H₂O molecules remain H₂O while their arrangement and motion change.
Tarjeta 184
Pregunta
How is the limiting reactant identified from given amounts?
Respuesta
Convert each reactant to the same product amount using the balanced equation; the smaller product amount identifies the limiting reactant.
Tarjeta 185
Pregunta
How does an endpoint differ from an equivalence point?
Respuesta
The endpoint is an observed signal such as indicator color change; the equivalence point is the exact stoichiometric condition.
Tarjeta 186
Pregunta
How is complete combustion of a hydrocarbon in excess oxygen classified, and what products form?
Respuesta
It is a redox combustion reaction that forms CO₂ and H₂O.
Tarjeta 187
Pregunta
What are the conjugate acid and conjugate base in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
Respuesta
NH₄⁺ is the conjugate acid of NH₃, and OH⁻ is the conjugate base of H₂O.
Tarjeta 188
Pregunta
What does reduction mean in a redox reaction?
Respuesta
Gain of electrons and a decrease in oxidation number.
Tarjeta 189
Pregunta
Which common changes are physical rather than chemical?
Respuesta
Phase changes and the formation or separation of mixtures are physical when each substance keeps its composition.
Tarjeta 190
Pregunta
How are strong soluble electrolytes written in a complete ionic equation?
Respuesta
As separated aqueous ions; solids, liquids, gases, and weak electrolytes stay intact.
Tarjeta 191
Pregunta
A diagram starts with six A particles and four B₂ particles for 2A + B₂ → 2AB; what remains after completion?
Respuesta
One B₂ remains. Six A consume three B₂ and form six AB.
Tarjeta 192
Pregunta
Why is dissolving NaCl in water normally classified as a physical change?
Respuesta
Na⁺ and Cl⁻ separate and become hydrated, but retain their chemical identities. Removing the water recovers NaCl; the shift from ion–ion to ion–dipole attractions does not by itself form a new substance.
Tarjeta 193
Pregunta
What mass of AgCl can form from 25.0 mL of 0.200 M AgNO₃ mixed with excess Cl⁻?
Respuesta
0.717 g AgCl. The 1:1 reaction gives 0.00500 mol AgCl; multiply by 143.32 g mol^-1.
Tarjeta 194
Pregunta
What calculation finds unknown analyte moles at equivalence?
Respuesta
Use titrant moles, n = MV, then apply the balanced-reaction mole ratio.
Tarjeta 195
Pregunta
Which feature identifies an acid–base, redox, or precipitation reaction?
Respuesta
Acid–base reactions transfer protons, redox reactions change oxidation numbers through electron transfer, and precipitation reactions form a sparingly soluble solid.
Tarjeta 196
Pregunta
What is the net ionic equation for strong acid–strong base neutralization?
Respuesta
H⁺(aq) + OH⁻(aq) → H₂O(l).
Tarjeta 197
Pregunta
What is the oxidation number of sulfur in SO₄²⁻?
Respuesta
+6. Four oxygens contribute -8 total, so sulfur must be +6 to give -2 overall.
Tarjeta 198
Pregunta
Why can gas bubbles alone be ambiguous evidence of reaction?
Respuesta
Bubbles may also come from boiling or dissolved gas escaping, so the context and particle identities must support a chemical change.
Tarjeta 199
Pregunta
How is melting ice represented as a balanced physical-change equation?
Respuesta
H₂O(s) → H₂O(l). The formula and atom count stay the same because only the physical state changes.
Tarjeta 200
Pregunta
What does a particle diagram show when no reaction occurs after two aqueous ionic solutions mix?
Respuesta
All ions remain separated and solvated, with no new bonded particles, precipitate, or gas.
Tarjeta 201
Pregunta
Why is rusting iron a chemical change?
Respuesta
Iron atoms form new iron-oxide substances through electron transfer and new bonding.
Tarjeta 202
Pregunta
For 2H₂O₂(aq) → 2H₂O(l) + O₂(g), what volume of O₂ forms from 0.100 mol H₂O₂ at 298 K and 1.00 atm?
Respuesta
1.22 L O₂. The mole ratio gives 0.0500 mol O₂, then V = nRT/P.
Tarjeta 203
Pregunta
A 25.0 mL monoprotic acid sample requires 20.0 mL of 0.150 M NaOH; what is the acid concentration?
Respuesta
0.120 M. At 1:1 equivalence, moles acid = 0.0200 L × 0.150 M, then divide by 0.0250 L.
Tarjeta 204
Pregunta
Which salts does the minimum solubility rule in this deck treat as soluble?
Respuesta
All salts containing Na⁺, K⁺, NH₄⁺, or NO₃⁻ are treated as soluble in water.
Tarjeta 205
Pregunta
How are the strengths of a conjugate acid and its conjugate base related?
Respuesta
A stronger acid has a weaker conjugate base, and a stronger base has a weaker conjugate acid.
Tarjeta 206
Pregunta
How are oxidation and reduction half-reactions combined into one balanced equation?
Respuesta
Multiply them so electrons lost equal electrons gained, add the half-reactions, then cancel electrons and any identical species on both sides.
Tarjeta 207
Pregunta
How do molecular, complete ionic, and net ionic equations differ?
Respuesta
Molecular equations keep compounds intact, complete ionic equations split strong soluble electrolytes, and net ionic equations remove spectators. All three conserve atoms and charge.
Tarjeta 208
Pregunta
How should coefficients change particle counts in a reaction diagram?
Respuesta
They set whole-particle ratios while preserving each particle's chemical formula.
Tarjeta 209
Pregunta
Is separating a mixture by distillation a chemical or physical change?
Respuesta
A physical change. Components change phase and location but keep their chemical identities.
Tarjeta 210
Pregunta
What equation results from Cu → Cu²⁺ + 2e⁻ and Ag⁺ + e⁻ → Ag?
Respuesta
Cu + 2Ag⁺ → Cu²⁺ + 2Ag. Multiply the silver half-reaction by 2 and cancel 2e⁻; both atom counts and net charge then match.
Tarjeta 211
Pregunta
How is average reaction rate found from a reactant concentration?
Respuesta
Use the negative concentration change divided by elapsed time, adjusted by its stoichiometric coefficient when comparing species rates.
Tarjeta 212
Pregunta
What does a rate law express?
Respuesta
It shows how the measured rate depends on reactant concentrations. In rate = k[A]^m[B]^n, m and n are the orders in A and B, and m + n is the overall order.
Tarjeta 213
Pregunta
A plot of ln[A] versus time is linear; what is the order in A and its integrated rate law?
Respuesta
First order: ln[A]t = ln[A]0 − kt, so the plot's slope is −k.
Tarjeta 214
Pregunta
What is an elementary reaction?
Respuesta
A single step in a mechanism whose rate law follows directly from its reactant molecularity.
Tarjeta 215
Pregunta
What two collision conditions are needed for reaction?
Respuesta
Sufficient collision energy and a productive molecular orientation.
Tarjeta 216
Pregunta
What does activation energy represent on a reaction-energy profile?
Respuesta
The energy difference from the reactants to the transition state. The reaction coordinate tracks the step's structural progress, not elapsed time.
Tarjeta 217
Pregunta
What must the elementary steps of a valid mechanism do when added?
Respuesta
Cancel intermediates and reproduce the overall balanced reaction.
Tarjeta 218
Pregunta
How is a proposed mechanism tested against kinetics?
Respuesta
Its derived rate law must agree with the experimentally measured rate law.
Tarjeta 219
Pregunta
What does a pre-equilibrium approximation assume?
Respuesta
A fast reversible step reaches equilibrium before a later slow step consumes its intermediate.
Tarjeta 220
Pregunta
What does each peak on a multistep energy profile represent?
Respuesta
A transition state for one elementary step.
Tarjeta 221
Pregunta
How does a catalyst increase reaction rate?
Respuesta
It provides an alternate mechanism with a lower activation-energy pathway.
Tarjeta 222
Pregunta
Why does crushing a solid reactant usually increase its reaction rate?
Respuesta
Crushing increases exposed surface area, so more reactant particles can collide with the other reactant each second.
Tarjeta 223
Pregunta
How is reaction order found from initial-rate data?
Respuesta
Compare trials where one reactant concentration changes while the others stay constant, then match the rate factor to the concentration factor.
Tarjeta 224
Pregunta
A plot of [A] versus time is linear; what is the order in A and its integrated rate law?
Respuesta
Zero order: [A]t = [A]0 − kt, so the plot's slope is −k.
Tarjeta 225
Pregunta
What is the rate law for the elementary step 2A + B → products?
Respuesta
rate = k[A]²[B]. This inference is valid because the step is elementary.
450 tarjetas
Advanced High School Chemistry Flashcards: Complete 9-Part Course Review
Estudia este mazo gratisFlashcards se abrirá para que puedas empezar a estudiar.
Tarjeta 226
Pregunta
How does raising temperature change a Maxwell–Boltzmann energy distribution and reaction rate?
Respuesta
The distribution shifts and broadens toward higher energies, so a larger fraction of collisions exceeds the activation-energy threshold and can react.
Tarjeta 227
Pregunta
How is ΔH read from a reaction-energy profile?
Respuesta
ΔH = energy of products − energy of reactants.
Tarjeta 228
Pregunta
What is a reaction intermediate?
Respuesta
A species formed in one mechanism step and consumed in a later step, so it cancels from the overall equation.
Tarjeta 229
Pregunta
Why can't overall reaction coefficients usually supply rate-law exponents?
Respuesta
The overall equation hides the mechanism; exponents come from experiment unless the reaction is a stated elementary step.
Tarjeta 230
Pregunta
How does pre-equilibrium remove an intermediate from a rate law?
Respuesta
Use the fast-step equilibrium relation to express the intermediate concentration in terms of stable reactants.
Tarjeta 231
Pregunta
What does each valley between peaks represent on a multistep profile?
Respuesta
A reaction intermediate.
Tarjeta 232
Pregunta
Does a catalyst change ΔH or the equilibrium constant?
Respuesta
No. It changes the pathway and rates, not reactant/product energies or the equilibrium composition.
Tarjeta 233
Pregunta
For 2A → B, how are disappearance of A and appearance of B related?
Respuesta
Reaction rate = -(1/2)Δ[A]/Δt = Δ[B]/Δt.
Tarjeta 234
Pregunta
How do the units of k depend on a rate law's overall order?
Respuesta
They must make the rate unit M s^-1: zero order uses M s^-1, first order s^-1, and second order M^-1 s^-1.
Tarjeta 235
Pregunta
A plot of 1/[A] versus time is linear; what is the order in A and its integrated rate law?
Respuesta
Second order: 1/[A]t = 1/[A]0 + kt, so the plot's slope is +k.
Tarjeta 236
Pregunta
What is molecularity?
Respuesta
The number of reacting particles in an elementary step, such as unimolecular or bimolecular.
Tarjeta 237
Pregunta
How does raising temperature affect k in the qualitative Arrhenius model?
Respuesta
k increases, often sharply, because a larger fraction of collisions can reach the transition state. Arrhenius-equation calculations are outside this deck’s scope.
Tarjeta 238
Pregunta
A reactant falls from 0.80 M to 0.50 M in 30. s; what is its average disappearance rate to two significant figures?
Respuesta
0.010 M s^-1. Use -(0.50 − 0.80) M ÷ 30. s.
Tarjeta 239
Pregunta
How does a catalyst differ from an intermediate in a mechanism?
Respuesta
A catalyst is consumed early and regenerated later; an intermediate is formed early and consumed later.
Tarjeta 240
Pregunta
For 2NO₂ → NO₃ + NO (slow), followed by NO₃ + CO → NO₂ + CO₂ (fast), what rate law is predicted?
Respuesta
rate = k[NO₂]². The first step is elementary and rate-limiting, so its molecularity sets the observed rate law.
Tarjeta 241
Pregunta
On a multistep reaction-energy profile, which feature often identifies the rate-determining step?
Respuesta
The step with the largest activation barrier measured from its preceding valley to its peak.
Tarjeta 242
Pregunta
If changing [B] leaves rate unchanged, what is the order in B?
Respuesta
Zero order, so [B]^0 = 1 in the measured rate law.
Tarjeta 243
Pregunta
What mechanism changes can binding, acid–base, or surface catalysis introduce?
Respuesta
They can orient reactants, lower activation barriers, or create new bound, protonated, or deprotonated intermediates and elementary steps; the catalyst is regenerated.
Tarjeta 244
Pregunta
What is special about a first-order reaction's half-life?
Respuesta
It is constant and independent of starting concentration: t1/2 = ln 2/k. Radioactive decay is a common first-order example.
Tarjeta 245
Pregunta
Why is a termolecular elementary collision uncommon?
Respuesta
Three particles must collide simultaneously with suitable energy and orientation, which is much less probable than one- or two-particle events.
Tarjeta 246
Pregunta
On a reaction-energy profile, how are reverse activation energy, forward activation energy, and ΔH related?
Respuesta
Ea,reverse = Ea,forward − ΔH. The reverse barrier is measured from products to the same transition state.
Tarjeta 247
Pregunta
Why can correct orientation matter even above the activation energy?
Respuesta
The colliding reactive sites must align so old bonds can break and new bonds can form along the reaction pathway.
Tarjeta 248
Pregunta
How does detecting a proposed reaction intermediate affect a mechanism claim?
Respuesta
It supports a mechanism that contains that intermediate, but it doesn't prove that mechanism is unique.
Tarjeta 249
Pregunta
For 2NO ⇌ N₂O₂ (fast equilibrium), followed by N₂O₂ + O₂ → 2NO₂ (slow), what observed rate law results?
Respuesta
rate = kobs[NO]²[O₂]. Start with rate = k₂[N₂O₂][O₂], use [N₂O₂] = K[NO]² from the fast equilibrium, then substitute.
Tarjeta 250
Pregunta
What does the highest point of a one-step energy profile represent?
Respuesta
The transition state, an unstable arrangement at the top of the activation barrier.
Tarjeta 251
Pregunta
What sign does q have for an endothermic system?
Respuesta
Positive, because the system absorbs heat from the surroundings.
Tarjeta 252
Pregunta
How does an exothermic reaction appear on an enthalpy diagram?
Respuesta
Products lie below reactants, so ΔH is negative.
Tarjeta 253
Pregunta
What condition defines thermal equilibrium?
Respuesta
Objects in contact have the same temperature, so there is no net heat transfer.
Tarjeta 254
Pregunta
What equations relate heat capacity and temperature change to heat transfer?
Respuesta
Use q = mcΔT with specific heat capacity, or q = nCₘΔT with molar heat capacity.
Tarjeta 255
Pregunta
Why is temperature constant during a phase-change plateau?
Respuesta
Added or removed energy changes interparticle potential energy instead of average kinetic energy.
Tarjeta 256
Pregunta
What does ΔHrxn describe?
Respuesta
The heat absorbed or released at constant pressure for the reaction exactly as written under the stated conditions.
Tarjeta 257
Pregunta
How is reaction enthalpy estimated from average bond enthalpies?
Respuesta
ΔHrxn ≈ Σ(bonds broken) − Σ(bonds formed).
Tarjeta 258
Pregunta
What is the standard enthalpy of formation of an element in its standard state?
Respuesta
Zero by definition.
Tarjeta 259
Pregunta
In a Hess’s law calculation, how should a step change when the target needs twice its reverse?
Respuesta
Reverse the equation, double every coefficient, and multiply its ΔH by -2.
Tarjeta 260
Pregunta
How can energy cross a system boundary during a process?
Respuesta
As heat or work. Heat transferred to or work done on the system increases its energy; heat transferred from or work done by the system decreases it.
Tarjeta 261
Pregunta
How does an endothermic reaction appear on an enthalpy diagram?
Respuesta
Products lie above reactants, so ΔH is positive.
Tarjeta 262
Pregunta
How are heat gained by a system and heat lost by its surroundings related in an isolated setup?
Respuesta
qsystem = -qsurroundings.
Tarjeta 263
Pregunta
In coffee-cup calorimetry, how is reaction heat related to solution heat?
Respuesta
qrxn = -qsolution when calorimeter heat is negligible and pressure is constant.
Tarjeta 264
Pregunta
What heat is required to melt n moles at the melting point?
Respuesta
q = nΔHfus.
Tarjeta 265
Pregunta
How does reversing a reaction change ΔH?
Respuesta
It reverses the sign of ΔH.
Tarjeta 266
Pregunta
Why is breaking a bond endothermic?
Respuesta
Energy must be supplied to separate atoms against their bonding attraction.
Tarjeta 267
Pregunta
How is ΔH°rxn calculated from standard enthalpies of formation?
Respuesta
ΣνΔHf°(products) − ΣνΔHf°(reactants).
Tarjeta 268
Pregunta
How does multiplying an equation by 3 affect its ΔH?
Respuesta
Multiply ΔH by 3 because enthalpy change scales with reaction amount.
Tarjeta 269
Pregunta
Why can an exothermic dissolution warm the solution?
Respuesta
The solution warms because forming solute–solvent attractions releases more energy than is absorbed in separating the original particles. The net potential-energy decrease raises particle kinetic energy and temperature.
Tarjeta 270
Pregunta
Does an energy diagram's activation barrier determine ΔH?
Respuesta
No. ΔH depends on reactant and product energy levels, while the barrier controls kinetics.
Tarjeta 271
Pregunta
Why does heat flow from a warmer object to a cooler object?
Respuesta
Energy transfers through collisions until their average kinetic energies, and therefore temperatures, equalize.
Tarjeta 272
Pregunta
How much heat warms 100.0 g of water by 5.0°C?
Respuesta
2.1 kJ. Use q = (100.0 g)(4.184 J g^-1 °C^-1)(5.0°C).
Tarjeta 273
Pregunta
How are the molar enthalpies of a phase change and its reverse related?
Respuesta
They have equal magnitudes and opposite signs, such as ΔHcond = -ΔHvap and ΔHfreeze = -ΔHfus.
Tarjeta 274
Pregunta
How does doubling every coefficient in a thermochemical equation affect ΔH?
Respuesta
It doubles ΔH.
Tarjeta 275
Pregunta
Why is forming a bond exothermic?
Respuesta
Atoms move to a lower-potential-energy bonded arrangement and release energy.
Tarjeta 276
Pregunta
What formation equation defines ΔHf° for CO₂(g)?
Respuesta
C(s, graphite) + O₂(g) → CO₂(g), forming exactly one mole from elements in standard states.
Tarjeta 277
Pregunta
What should happen to intermediate species when equations in a Hess’s law calculation are added?
Respuesta
They cancel, leaving the target overall reaction.
Tarjeta 278
Pregunta
If the surroundings warm during a process, what is the likely sign of qsystem?
Respuesta
Negative; the system likely released heat to the surroundings.
Tarjeta 279
Pregunta
For a profile with reactants at 40 kJ and products at 10 kJ, what is ΔH?
Respuesta
-30 kJ for the reaction as drawn.
Tarjeta 280
Pregunta
Assuming no phase change, what determines the final temperature when two substances exchange heat in an insulated container?
Respuesta
Energy conservation: q_warm + q_cool = 0. Use each substance's mass, heat capacity, and initial temperature to solve for the common final temperature.
Tarjeta 281
Pregunta
How would heat loss to the room affect an exothermic calorimetry result?
Respuesta
The observed temperature rise is too small, so the calculated magnitude of released heat is too low.
Tarjeta 282
Pregunta
What heat expression covers warming a liquid without a phase change?
Respuesta
q = mcΔT, not nΔHphase.
Tarjeta 283
Pregunta
If forming 1 mol of product has ΔH = -50 kJ mol^-1, what is q when 2 mol forms?
Respuesta
-100 kJ. Use q = nΔH = (2 mol)(-50 kJ mol^-1).
Tarjeta 284
Pregunta
Breaking reactant bonds requires 500 kJ, and forming product bonds releases 650 kJ; what is the estimated ΔH?
Respuesta
-150 kJ, from 500 − 650.
Tarjeta 285
Pregunta
For CO(g) + ½O₂(g) → CO₂(g), what is ΔH°rxn if ΔHf°[CO] = -110.5 and ΔHf°[CO₂] = -393.5 kJ mol^-1?
Respuesta
-283.0 kJ. Use -393.5 - [-110.5 + ½(0)], since ΔHf°[O₂(g)] = 0.
Tarjeta 286
Pregunta
In a Hess’s law calculation, two valid steps have ΔH values +25 kJ and -60 kJ; what is the combined ΔH?
Respuesta
-35 kJ, provided the equations add to the target reaction.
Tarjeta 287
Pregunta
Why is “bonds breaking releases energy” incorrect?
Respuesta
Bond breaking absorbs energy; the overall reaction releases energy only when forming new bonds releases more than breaking old bonds requires.
Tarjeta 288
Pregunta
How would melting appear on an energy diagram?
Respuesta
The liquid lies above the solid, so ΔHfus is positive; the diagram represents a physical, endothermic change.
Tarjeta 289
Pregunta
Can two objects at the same temperature exchange energy microscopically?
Respuesta
Yes, but their energy transfers balance, so there is no net heat flow.
Tarjeta 290
Pregunta
Why must the calorimeter's heat capacity be included when it isn't negligible?
Respuesta
The apparatus can absorb or release heat, so include q_cal = C_calΔT in the energy balance: q_process + q_solution + q_cal = 0.
Tarjeta 291
Pregunta
What makes chemical equilibrium dynamic?
Respuesta
Forward and reverse reactions continue at equal rates even though macroscopic concentrations stay constant.
Tarjeta 292
Pregunta
For aA + bB ⇌ cC, what is the concentration-form expression for Q?
Respuesta
Q = [C]^c / ([A]^a[B]^b), using current rather than necessarily equilibrium concentrations.
Tarjeta 293
Pregunta
What does K much greater than 1 indicate?
Respuesta
Products predominate at equilibrium, though K says nothing about reaction speed.
Tarjeta 294
Pregunta
How does reversing a reaction change its equilibrium constant?
Respuesta
K becomes 1/K.
Tarjeta 295
Pregunta
Can a reversible system reach equilibrium when it starts with only products?
Respuesta
Yes, if the reverse reaction is possible. The equilibrium composition depends on temperature, initial amounts, and volume or pressure.
Tarjeta 296
Pregunta
How do Q and K predict reaction direction?
Respuesta
Q < K shifts forward, Q > K shifts reverse, and Q = K means equilibrium.
Tarjeta 297
Pregunta
Which species are omitted from a heterogeneous equilibrium expression?
Respuesta
Pure solids and pure liquids because their activities are effectively constant.
Tarjeta 298
Pregunta
How does increasing a dissolved reactant's concentration or a gaseous reactant's partial pressure affect equilibrium at constant temperature when other Q terms are initially unchanged?
Respuesta
It lowers Q relative to K, so the system shifts toward products until Q = K again. Changing the amount of a pure solid or liquid omitted from Q does not cause this shift while that pure phase remains present.
Tarjeta 299
Pregunta
What does a flat concentration-time graph mean at equilibrium?
Respuesta
Each concentration is constant, not necessarily equal to the others.
Tarjeta 300
Pregunta
For A ⇌ B in one fixed volume, a particulate model shows 16 A and 0 B initially, then 4 A and 12 B at equilibrium. What changed, what predominates, and what is Kc?
Respuesta
The net change was forward: 12 A particles became 12 B particles. B predominates at equilibrium, and Kc = [B]/[A] = 12/4 = 3.0 because both counts come from the same fixed volume.
Tarjeta 301
Pregunta
What can Ksp tell you about a salt's solubility, and when can two Ksp values be compared directly?
Respuesta
Ksp > 1 indicates a soluble salt. For salts with the same dissolution stoichiometry, a larger Ksp generally means greater molar solubility; across different stoichiometries, calculate molar solubility before comparing.
Tarjeta 302
Pregunta
What is the common-ion effect on solubility?
Respuesta
Adding an ion already in the dissolution equilibrium usually decreases the solid's molar solubility.
Tarjeta 303
Pregunta
How does uniform dilution shift an aqueous equilibrium based on the stoichiometric powers in Q?
Respuesta
It shifts toward the side with the larger sum of stoichiometric coefficients for dissolved species included in Q. If the sums are equal, dilution causes no shift by this effect; pure solids and liquids remain omitted.
Tarjeta 304
Pregunta
What happens if a reversible reaction starts with reactants only?
Respuesta
The forward rate is initially largest; products form, the reverse rate grows, and the rates eventually become equal.
Tarjeta 305
Pregunta
What is the purpose of an ICE table?
Respuesta
To organize initial, change, and equilibrium concentrations using reaction stoichiometry.
Tarjeta 306
Pregunta
Can a reaction with a very large K be slow?
Respuesta
Yes. K describes thermodynamic equilibrium position, while rate depends on kinetics and activation energy.
Tarjeta 307
Pregunta
What happens to Q immediately after product concentration increases?
Respuesta
Q increases; if it rises above K, the reaction shifts toward reactants.
Tarjeta 308
Pregunta
How does multiplying every reaction coefficient by 2 affect K?
Respuesta
The new equilibrium constant is K².
Tarjeta 309
Pregunta
For A ⇌ B, Kc = 4.0 and initially [A] = 1.0 M and [B] = 0, what are the equilibrium concentrations?
Respuesta
[A] = 0.20 M and [B] = 0.80 M. Let x form: Kc = x/(1.0 − x) = 4.0, so x = 0.80 M.
Tarjeta 310
Pregunta
What macroscopic properties stay constant at equilibrium?
Respuesta
Properties such as concentration, color, and pressure remain constant when external conditions are fixed.
Tarjeta 311
Pregunta
How does decreasing volume shift a gaseous equilibrium?
Respuesta
Toward the side with fewer moles of gas, if the two sides have different gaseous mole counts.
Tarjeta 312
Pregunta
For N₂ + 3H₂ ⇌ 2NH₃, what is Kc?
Respuesta
Kc = [NH₃]² / ([N₂][H₂]³).
Tarjeta 313
Pregunta
For CaF₂(s) ⇌ Ca²⁺ + 2F⁻, how is Ksp written in terms of molar solubility s in pure water?
Respuesta
Ksp = s(2s)² = 4s³ because [Ca²⁺] = s and [F⁻] = 2s.
Tarjeta 314
Pregunta
What does K much less than 1 indicate?
Respuesta
Reactants predominate at equilibrium.
Tarjeta 315
Pregunta
How does decreasing a dissolved product's concentration or a gaseous product's partial pressure affect equilibrium when other Q terms are initially unchanged?
Respuesta
It lowers Q and drives a net forward reaction until equilibrium returns. Changing the amount of a pure solid or liquid omitted from Q does not cause this shift while that phase remains.
Tarjeta 316
Pregunta
Does equilibrium mean the reaction has stopped?
Respuesta
No. Both directions continue, but equal rates produce no net macroscopic change.
Tarjeta 317
Pregunta
Why does adding NaF reduce CaF₂ solubility?
Respuesta
The added F⁻ raises Qsp, shifting the dissolution equilibrium toward solid CaF₂.
Tarjeta 318
Pregunta
For N₂ + 3H₂ ⇌ 2NH₃, what is Kp when P_N₂ = 0.50 atm, P_H₂ = 1.50 atm, and P_NH₃ = 0.25 atm?
Respuesta
0.037. Use Kp = (P_NH₃)²/[(P_N₂)(P_H₂)³] = (0.25)²/[(0.50)(1.50)³]. Use equilibrium partial pressures directly; Kc↔Kp conversion isn't assessed.
Tarjeta 319
Pregunta
What happens to Q when a gaseous equilibrium mixture is compressed at constant temperature if products have fewer gas moles?
Respuesta
Q falls relative to K, so the reaction shifts toward products.
Tarjeta 320
Pregunta
How do K and Q transform when a reaction is reversed, its coefficients are multiplied, or reactions are added?
Respuesta
They follow the same algebra: reversing takes the reciprocal, multiplying every coefficient by c raises the value to the power c, and adding reactions multiplies their K or Q values.
Tarjeta 321
Pregunta
When is the small-x approximation acceptable?
Respuesta
When x is small relative to the initial concentration and the final result confirms the neglected change is suitably small.
Tarjeta 322
Pregunta
What graph feature shows a disturbance followed by re-equilibration?
Respuesta
A sudden or gradual concentration change followed by new constant plateaus while rates return to equality.
Tarjeta 323
Pregunta
If Q = 0.20 and K = 5.0, which direction is favored next?
Respuesta
Forward, because Q < K.
Tarjeta 324
Pregunta
At equilibrium, are reactant and product concentrations equal?
Respuesta
Not necessarily. They are constant, while forward and reverse rates are equal.
Tarjeta 325
Pregunta
CaF₂ has Ksp = 3.2 × 10^-11 in pure water; what is its molar solubility?
Respuesta
2.0 × 10^-4 M. If the molar solubility is s, then [Ca²⁺] = s, [F⁻] = 2s, and Ksp = 4s³.
Tarjeta 326
Pregunta
For N₂ + 3H₂ ⇌ 2NH₃, how is Qp written?
Respuesta
Qp = (P_NH₃)²/[(P_N₂)(P_H₂)³], using the current partial pressures rather than necessarily equilibrium values.
Tarjeta 327
Pregunta
How does heating shift an endothermic forward reaction?
Respuesta
Toward products, and K increases because temperature changes the equilibrium constant.
Tarjeta 328
Pregunta
Why do both forward and reverse rates change as equilibrium is approached?
Respuesta
As reactant and product concentrations change, the collision frequencies for the two directions change until their rates match.
Tarjeta 329
Pregunta
CaF₂ has Ksp = 3.2 × 10^-11. What is its molar solubility in 0.10 M NaF?
Respuesta
About 3.2 × 10^-9 M. With [F⁻] ≈ 0.10 M, Ksp = [Ca²⁺][F⁻]² gives s = (3.2 × 10^-11)/(0.10)². The common ion lowers solubility but does not change Ksp at constant temperature.
Tarjeta 330
Pregunta
What concentration data must be used to calculate Kc?
Respuesta
Equilibrium concentrations, each raised to its stoichiometric coefficient and excluding pure solids and liquids.
Tarjeta 331
Pregunta
What is a Brønsted–Lowry acid?
Respuesta
A proton donor.
Tarjeta 332
Pregunta
How is pH defined?
Respuesta
pH = -log[H₃O⁺].
Tarjeta 333
Pregunta
What is Ka for HA + H₂O ⇌ H₃O⁺ + A⁻?
Respuesta
Ka = [H₃O⁺][A⁻]/[HA].
Tarjeta 334
Pregunta
How does stabilizing a base affect its basicity and the strength of its conjugate acid?
Respuesta
It makes the base weaker and its conjugate acid stronger. A more stable base is less willing to accept H⁺.
Tarjeta 335
Pregunta
What is a Brønsted–Lowry base?
Respuesta
A proton acceptor.
Tarjeta 336
Pregunta
At 25°C, what are Kw and the relationship between pH and pOH?
Respuesta
Kw = [H₃O⁺][OH⁻] = 1.0 × 10^-14. Taking negative logarithms gives pH + pOH = 14.00.
Tarjeta 337
Pregunta
What is Kb for B + H₂O ⇌ BH⁺ + OH⁻?
Respuesta
Kb = [BH⁺][OH⁻]/[B].
Tarjeta 338
Pregunta
Why can lowering pH increase the solubility of a salt containing a basic anion?
Respuesta
H₃O⁺ consumes the anion, pulling the dissolution equilibrium toward more dissolved ions.
Tarjeta 339
Pregunta
What are conjugate acid–base pairs?
Respuesta
Species that differ by exactly one proton.
Tarjeta 340
Pregunta
What is the pH of 1.0 × 10^-3 M HCl?
Respuesta
3.00, assuming complete dissociation and negligible water contribution.
Tarjeta 341
Pregunta
How are pKa and pKb defined?
Respuesta
pKa = -log Ka, and pKb = -log Kb.
Tarjeta 342
Pregunta
Why does acid strength increase across a row of comparable hydrides?
Respuesta
Increasing electronegativity stabilizes the conjugate base and polarizes the H–A bond.
Tarjeta 343
Pregunta
What is an amphiprotic species?
Respuesta
A species that can donate or accept a proton, such as HCO₃⁻.
Tarjeta 344
Pregunta
What amounts remain after a limited amount of strong base partially neutralizes weak acid HA?
Respuesta
Subtract the reacted moles from HA and form the same number of moles of A⁻. The result gives the remaining HA and formed A⁻ amounts before any equilibrium or buffer-pH calculation.
Tarjeta 345
Pregunta
How are Ka, Kb, pKa, and pKb related for a conjugate pair at 25°C?
Respuesta
KaKb = Kw = 1.0 × 10^-14, and pKa + pKb = pKw = 14.00.
Tarjeta 346
Pregunta
When does pH have little effect on a salt's solubility?
Respuesta
When neither dissolved ion reacts appreciably with H₃O⁺ or OH⁻.
Tarjeta 347
Pregunta
How does H₂O act in HCl + H₂O → H₃O⁺ + Cl⁻ and in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
Respuesta
It acts as a base in the first reaction by accepting H⁺, and as an acid in the second by donating H⁺.
Tarjeta 348
Pregunta
After mixing weak base B with strong acid, what controls the final solution in the three stoichiometric regimes?
Respuesta
Excess B leaves a B/BH⁺ buffer; equimolar amounts leave BH⁺, so the solution is acidic; excess strong acid sets the pH from the remaining H₃O⁺.
Tarjeta 349
Pregunta
What two components make a typical weak-acid buffer?
Respuesta
A weak acid and a significant amount of its conjugate base.
Tarjeta 350
Pregunta
What do the successive half-equivalence pH values approximate in a diprotic weak-acid titration?
Respuesta
The first approximates pKa₁ and the second approximates pKa₂ because each conjugate pair has equal concentrations at its half-equivalence point.
Tarjeta 351
Pregunta
Which acid is stronger, one with pKa 2 or pKa 5?
Respuesta
The acid with pKa 2; lower pKa means larger Ka.
Tarjeta 352
Pregunta
What is the Henderson–Hasselbalch equation?
Respuesta
pH = pKa + log([A⁻]/[HA]).
Tarjeta 353
Pregunta
Why are larger binary hydrides down a group often stronger acids?
Respuesta
The H–A bond becomes weaker as the central atom grows, so proton release is easier.
Tarjeta 354
Pregunta
What mainly determines buffer capacity?
Respuesta
The concentrations of both members of the conjugate acid–base pair. Increasing both concentrations at a fixed ratio increases capacity without changing pH; capacity is best balanced for added acid and base when their concentrations are similar.
Tarjeta 355
Pregunta
Why does acid increase CaCO₃ solubility?
Respuesta
H₃O⁺ converts CO₃²⁻ to HCO₃⁻ or carbonic acid species, reducing free carbonate and driving more CaCO₃ to dissolve.
Tarjeta 356
Pregunta
What does pH < pKa imply for a weak-acid pair?
Respuesta
The protonated form HA predominates over A⁻.
Tarjeta 357
Pregunta
What happens when stoichiometrically equal amounts of a monoprotic weak acid and strong base are mixed?
Respuesta
The weak acid is consumed to its conjugate base; at equivalence, the solution isn't a buffer containing both forms.
Tarjeta 358
Pregunta
What is [H₃O⁺] when pH = 4.50?
Respuesta
3.2 × 10^-5 M, from [H₃O⁺] = 10^-pH.
Tarjeta 359
Pregunta
What is the pH of 0.010 M Ba(OH)₂ at 25°C?
Respuesta
About 12.30. Complete dissociation gives [OH⁻] = 0.020 M, so pOH = 1.70. At 25°C, pH + pOH = 14.00, so pH = 12.30.
Tarjeta 360
Pregunta
How does a buffer respond to a small amount of added strong acid?
Respuesta
Its conjugate base consumes H⁺, converting to the weak acid and limiting the pH change.
Tarjeta 361
Pregunta
Why is the equivalence-point solution basic in a monoprotic weak-acid–strong-base titration?
Respuesta
The conjugate base produced at equivalence reacts with water to form OH⁻, so the pH is above neutral—above 7.00 at 25°C.
Tarjeta 362
Pregunta
How is percent ionization calculated for a weak acid or weak base?
Respuesta
For HA, use ([H₃O⁺]equilibrium ÷ [HA]initial) × 100%. For B, use ([BH⁺]equilibrium ÷ [B]initial) × 100%, under the usual monoprotic setup.
Tarjeta 363
Pregunta
When is Henderson–Hasselbalch useful for an initial buffer-pH calculation?
Respuesta
Use it when both members of a conjugate acid–base pair are present in meaningful amounts, including after in-scope stoichiometry creates a buffer. Calculating the pH change after acid or base is added to an existing buffer is outside this deck’s scope.
Tarjeta 364
Pregunta
Why does adding oxygen atoms usually strengthen oxyacids with the same central atom?
Respuesta
Extra oxygens withdraw electron density and delocalize negative charge in the conjugate base.
Tarjeta 365
Pregunta
A prepared buffer is accidentally diluted to twice its intended volume; what happens to its pH and capacity?
Respuesta
Its pH stays nearly the same, and its capacity per liter is halved because both component concentrations halve. The total neutralizing moles in the sample remain unchanged.
Tarjeta 366
Pregunta
How does adding OH⁻ affect Mg(OH)₂ solubility?
Respuesta
It decreases solubility through the common-ion effect, shifting Mg(OH)₂(s) ⇌ Mg²⁺ + 2OH⁻ toward the solid.
Tarjeta 367
Pregunta
A buffer has equal [A⁻] and [HA]; what is its pH?
Respuesta
pH = pKa because log(1) = 0.
Tarjeta 368
Pregunta
How should a weak acid–strong base mixture be solved before equivalence?
Respuesta
First use mole stoichiometry; if both HA and A⁻ remain, use the resulting buffer relation.
Tarjeta 369
Pregunta
Why can pure neutral water have a pH other than 7.00?
Respuesta
Kw changes with temperature. Neutrality means [H₃O⁺] = [OH⁻], while pH = 7.00 only when Kw = 1.0 × 10^-14 at 25°C.
Tarjeta 370
Pregunta
25.0 mL of 0.200 M HCl is diluted to 100.0 mL; what is the pH?
Respuesta
1.301. Dilution gives [H₃O⁺] = (0.200 M)(25.0 mL)/(100.0 mL) = 0.0500 M, so pH = -log(0.0500).
Tarjeta 371
Pregunta
How does a buffer respond to a small amount of added strong base?
Respuesta
The weak acid consumes OH⁻, forming conjugate base and water.
Tarjeta 372
Pregunta
How do you find the final pH after mixing a strong acid and strong base at 25°C?
Respuesta
Use H₃O⁺ + OH⁻ → 2H₂O and compare their moles. Divide excess H₃O⁺ or OH⁻ by the total volume, then calculate pH or pOH from that excess concentration. Equal moles give pH 7.00 at 25°C.
Tarjeta 373
Pregunta
What distinguishes acid strength from acid concentration?
Respuesta
Strength is the equilibrium tendency to donate H⁺, reflected by Ka or pKa; concentration is the amount of acid per solution volume.
Tarjeta 374
Pregunta
If [A⁻]/[HA] = 10, how does pH compare with pKa?
Respuesta
pH = pKa + 1 because log 10 = 1.
Tarjeta 375
Pregunta
Which conjugate base is more stable, one with localized or resonance-delocalized charge?
Respuesta
The resonance-delocalized conjugate base, which generally corresponds to the stronger acid.
Tarjeta 376
Pregunta
Which 1.0 L buffer has greater capacity: 1.0 mol each of HA/A⁻ or 0.10 mol each at the same ratio?
Respuesta
The 1.0 mol pair; both have the same initial pH, but the larger amounts neutralize more added acid or base.
Tarjeta 377
Pregunta
For BHX(s) ⇌ BH⁺ + X⁻, why can raising pH increase the salt's solubility?
Respuesta
OH⁻ consumes BH⁺ to form B and H₂O, so dissolution shifts right to replace BH⁺. This is a qualitative prediction, not a pH-dependent solubility calculation.
Tarjeta 378
Pregunta
What does pH > pKa imply for a weak-acid pair?
Respuesta
The deprotonated form A⁻ predominates over HA.
Tarjeta 379
Pregunta
For HA + B ⇌ A⁻ + BH⁺, which side is favored when pKa(HA) = 4 and pKa(BH⁺) = 9?
Respuesta
Products are favored. Proton transfer moves toward the weaker acid–base pair, and K ≈ 10^(9 − 4) = 10^5.
Tarjeta 380
Pregunta
What is the pOH when [OH⁻] = 2.5 × 10^-4 M?
Respuesta
3.60, from -log(2.5 × 10^-4).
Tarjeta 381
Pregunta
What is the pH of 0.100 M HA when Ka = 1.0 × 10^-5?
Respuesta
About 3.00. The ICE setup gives Ka = x²/(0.100 − x); x ≈ 1.0 × 10^-3 M, and the 1.0% change validates the approximation.
Tarjeta 382
Pregunta
Why does a buffer fail after too much strong acid is added?
Respuesta
Its conjugate base is depleted, so added H⁺ is no longer consumed effectively.
Tarjeta 383
Pregunta
What do two clear equivalence regions on an acid titration curve suggest?
Respuesta
At least two distinguishable titratable protons; on a clean ideal curve with exactly two equivalence regions, this is consistent with a diprotic acid.
Tarjeta 384
Pregunta
A buffer has pKa 4.8 and [A⁻]/[HA] = 0.10; what is pH?
Respuesta
3.8, from 4.8 + log(0.10).
Tarjeta 385
Pregunta
Why is HCl stronger than HF in water despite F being more electronegative?
Respuesta
The H–F bond is much stronger; bond strength dominates this down-group binary-acid comparison.
Tarjeta 386
Pregunta
Why does percent ionization increase when a weak acid is diluted?
Respuesta
Dilution shifts ionization toward more particles, so a larger fraction ionizes even though [H₃O⁺] decreases.
Tarjeta 387
Pregunta
A buffer contains more HA than A⁻. Which addition can it neutralize in greater amount: strong acid or strong base?
Respuesta
Strong base. The larger HA reserve consumes more added OH⁻; a buffer with more A⁻ than HA instead has greater capacity for added strong acid.
Tarjeta 388
Pregunta
Why can removing a basic anion increase a salt's molar solubility without changing Ksp?
Respuesta
The equilibrium shifts to replace the consumed ion; Ksp remains fixed at the same temperature.
Tarjeta 389
Pregunta
Why can an acid–base indicator change color as pH changes?
Respuesta
Its protonated and deprotonated forms have different colors or other observable properties, and their relative amounts change with pH.
Tarjeta 390
Pregunta
What buffer results from mixing 1.0 mol HA with 0.40 mol OH⁻?
Respuesta
0.60 mol HA and 0.40 mol A⁻ remain, forming a buffer before any equilibrium calculation.
Tarjeta 391
Pregunta
What is the pH of 0.200 M weak base B when Kb = 2.0 × 10^-5 at 25°C?
Respuesta
About 11.30. The ICE setup gives Kb = x²/(0.200 − x); x ≈ 2.0 × 10^-3 M OH⁻, and the 1.0% change validates the approximation.
Tarjeta 392
Pregunta
Why does a weak acid alone not make an effective buffer?
Respuesta
It lacks a substantial conjugate-base reserve to consume added strong acid.
Tarjeta 393
Pregunta
What controls pH after excess strong base passes equivalence?
Respuesta
The concentration of excess OH⁻ after accounting for reaction stoichiometry and total volume.
Tarjeta 394
Pregunta
How should an indicator be chosen for a titration?
Respuesta
Its color-change range should fall within the steep pH change near the equivalence point.
Tarjeta 395
Pregunta
How can a measured pH and known pKa give a conjugate-base/acid ratio?
Respuesta
Rearrange Henderson–Hasselbalch: [A⁻]/[HA] = 10^(pH − pKa).
Tarjeta 396
Pregunta
Can a weak base and its conjugate acid form a buffer?
Respuesta
Yes, when both are present in significant amounts.
Tarjeta 397
Pregunta
For equal-volume buffers with the same conjugate-base/acid ratio, how does adding the same amount of strong acid affect a more concentrated versus less concentrated buffer?
Respuesta
The concentrated buffer changes pH less because it has greater capacity.
Tarjeta 398
Pregunta
How does equivalence-point pH compare for strong acid–strong base, weak acid–strong base, and weak base–strong acid titrations at 25°C?
Respuesta
Strong acid–strong base: pH 7.00. Weak acid–strong base: above 7.00 because the conjugate base reacts with water. Weak base–strong acid: below 7.00 because the conjugate acid reacts with water.
Tarjeta 399
Pregunta
Why should mole ratios replace concentration ratios after mixing buffer solutions?
Respuesta
Both components share the same final volume, so that volume cancels in [A⁻]/[HA].
Tarjeta 400
Pregunta
How does adding a little strong acid change a buffer's conjugate-base and conjugate-acid amounts?
Respuesta
The conjugate base decreases and its conjugate acid increases by the amount of strong acid consumed.
Tarjeta 401
Pregunta
What does entropy measure qualitatively?
Respuesta
The dispersal of matter and energy among available microstates.
Tarjeta 402
Pregunta
How is standard reaction entropy calculated?
Respuesta
ΔS°rxn = ΣνS°(products) − ΣνS°(reactants).
Tarjeta 403
Pregunta
What equation gives ΔG° from ΔH° and ΔS°, and what standard states do the degree symbols assume?
Respuesta
ΔG° = ΔH° − TΔS°. The standard states are pure substances, 1.0 M solutions, and gases at 1 atm or 1 bar; T is in kelvins and energy units must match.
Tarjeta 404
Pregunta
Does thermodynamic favorability guarantee a fast reaction?
Respuesta
No. A favorable reaction can be slow when its activation barrier is large.
Tarjeta 405
Pregunta
What is ΔG at equilibrium?
Respuesta
Zero under the current conditions because there is no net driving force.
Tarjeta 406
Pregunta
Why can an endothermic dissolution still be thermodynamically favorable?
Respuesta
A sufficiently positive entropy change can make TΔS exceed positive ΔH, giving negative ΔG.
Tarjeta 407
Pregunta
How can an unfavorable reaction be driven by a favorable one?
Respuesta
Couple them so their equations and ΔG values add to a negative overall ΔG.
Tarjeta 408
Pregunta
Where does oxidation occur in every electrochemical cell?
Respuesta
At the anode.
Tarjeta 409
Pregunta
How are standard cell potential and standard free energy related?
Respuesta
ΔG° = -nFE°cell.
Tarjeta 410
Pregunta
What equation gives cell potential under nonstandard conditions?
Respuesta
E = E° − (RT/nF) ln Q. When Q = 1, ln Q = 0, so E = E°.
Tarjeta 411
Pregunta
How is electrical charge related to current and time?
Respuesta
q = It.
Tarjeta 412
Pregunta
Which phase has greater molar entropy, liquid water or ice at the same temperature?
Respuesta
Liquid water because its molecules have more accessible arrangements and motion.
Tarjeta 413
Pregunta
Do elements in their standard states have zero standard molar entropy?
Respuesta
No. Their ΔHf° is zero, but their absolute S° values are positive above 0 K.
Tarjeta 414
Pregunta
How do the four ΔH° and ΔS° sign combinations determine thermodynamic favorability across temperature?
Respuesta
ΔH° < 0 and ΔS° > 0 is favorable at every temperature; ΔH° > 0 and ΔS° < 0 is thermodynamically unfavored at every temperature. If both are positive, favorability requires high temperature; if both are negative, it requires low temperature.
Tarjeta 415
Pregunta
What does it indicate when a thermodynamically favored process does not occur at a measurable rate?
Respuesta
It is under kinetic control, commonly because of a high activation energy; no measurable reaction does not mean the system is at equilibrium.
Tarjeta 416
Pregunta
How are ΔG° and K related?
Respuesta
ΔG° = -RT ln K.
Tarjeta 417
Pregunta
What two contributions compete in dissolving an ionic solid?
Respuesta
Enthalpy changes from separating and solvating particles, and entropy changes from their new dispersal and solvent organization.
Tarjeta 418
Pregunta
What must cancel when coupled reactions are added?
Respuesta
Shared intermediates, leaving the desired net reaction.
Tarjeta 419
Pregunta
Where does reduction occur in every electrochemical cell?
Respuesta
At the cathode.
Tarjeta 420
Pregunta
What sign of E°cell indicates a favorable standard galvanic reaction?
Respuesta
Positive E°cell, corresponding to negative ΔG°.
Tarjeta 421
Pregunta
If Q increases for a galvanic reaction, how does E change at fixed temperature?
Respuesta
E decreases according to the Nernst equation. Le Châtelier's principle does not apply to an operating cell away from equilibrium; use Q and Nernst reasoning instead.
Tarjeta 422
Pregunta
How are moles of electrons found from charge?
Respuesta
Moles e⁻ = q/F, where F ≈ 96485 C mol^-1 e⁻.
Tarjeta 423
Pregunta
How does producing more gas particles usually affect system entropy?
Respuesta
It increases entropy because the particles have more positional microstates.
Tarjeta 424
Pregunta
Can a dissolution with negative ΔH be unfavorable?
Respuesta
Yes. A sufficiently negative entropy change at the stated temperature can make ΔG positive.
Tarjeta 425
Pregunta
When can a process with ΔH > 0 and ΔS > 0 become favorable?
Respuesta
At sufficiently high temperature, when TΔS exceeds ΔH.
Tarjeta 426
Pregunta
How does a catalyst affect ΔG?
Respuesta
It does not change ΔG; it lowers the activation barrier for both directions.
Tarjeta 427
Pregunta
For A → B, ΔGf°(A) = -50 kJ mol^-1 and ΔGf°(B) = -80 kJ mol^-1. What is ΔG°rxn?
Respuesta
-30 kJ mol^-1. Use ΣνΔGf°(products) − ΣνΔGf°(reactants) = -80 − (-50).
Tarjeta 428
Pregunta
Why can dissolving a gas in a liquid have a negative entropy change?
Respuesta
Gas particles lose much of their translational freedom when confined and solvated in the liquid.
Tarjeta 429
Pregunta
If coupled steps have ΔG values +20 kJ and -35 kJ, what is overall ΔG?
Respuesta
-15 kJ, so the combined process is thermodynamically favorable under those conditions.
Tarjeta 430
Pregunta
What role does each half-cell solution play in an electrochemical cell?
Respuesta
It supplies dissolved redox species at an electrode interface and carries ions within its compartment. Separate compartments prevent direct mixing while the external circuit and salt bridge connect the half-cells.
Tarjeta 431
Pregunta
How is E°cell found from standard reduction potentials?
Respuesta
E°cell = E°cathode − E°anode, using both tabulated values as reductions.
Tarjeta 432
Pregunta
How does a cell's potential magnitude change as Q approaches or moves away from K, and what is E at equilibrium?
Respuesta
|E| falls toward zero as Q approaches K and grows as the system moves farther from equilibrium. At equilibrium, Q = K and E = 0.
Tarjeta 433
Pregunta
How many moles of electrons pass when 1.93 × 10^5 C flows?
Respuesta
2.00 mol e⁻, from q/F.
Tarjeta 434
Pregunta
How does a salt bridge maintain charge balance in a galvanic cell?
Respuesta
Anions migrate toward the anode compartment and cations toward the cathode compartment, countering the net charge imbalances created by the two half-reactions.
Tarjeta 435
Pregunta
Why does raising a substance's temperature generally increase its entropy?
Respuesta
Energy spreads across more accessible particle energy states, increasing the number of possible microscopic arrangements.
Tarjeta 436
Pregunta
When can a process with ΔH < 0 and ΔS < 0 be favorable?
Respuesta
At sufficiently low temperature, where the unfavorable -TΔS term is small.
Tarjeta 437
Pregunta
Why can diamond persist even though graphite is more stable at standard conditions?
Respuesta
Conversion has a large activation barrier, so diamond is kinetically persistent.
Tarjeta 438
Pregunta
What do the external circuit and measuring device do in an electrochemical cell?
Respuesta
The circuit carries electrons from anode to cathode; a voltmeter measures potential difference, while an ammeter in series measures current.
Tarjeta 439
Pregunta
At constant temperature, how does increasing the volume available to a gas affect its entropy?
Respuesta
Entropy increases because the gas particles can occupy more positions in the larger space, so more microstates are accessible.
Tarjeta 440
Pregunta
How does reversing one coupled reaction affect its ΔG?
Respuesta
It reverses the sign of that reaction's ΔG.
Tarjeta 441
Pregunta
Why is n required in ΔG° = -nFE°?
Respuesta
It is the moles of electrons transferred per balanced reaction, linking charge flow to reaction extent.
Tarjeta 442
Pregunta
What makes an electrolytic cell operate?
Respuesta
An external power source drives a thermodynamically unfavorable redox reaction; oxidation still occurs at the anode and reduction at the cathode.
Tarjeta 443
Pregunta
In an Mⁿ⁺/M concentration cell, which half-cell is the anode: the dilute or concentrated ion solution?
Respuesta
The dilute half-cell. Oxidation produces Mⁿ⁺ there, while reduction consumes Mⁿ⁺ in the concentrated half-cell, so electrons flow from dilute to concentrated as the concentrations move toward equality.
Tarjeta 444
Pregunta
How is deposited metal mass found from current and time?
Respuesta
Find q = It, convert q/F to moles e⁻, use the half-reaction ratio to moles metal, then multiply by molar mass.
Tarjeta 445
Pregunta
Given product S° total 500 J mol^-1 K^-1 and reactant total 420 J mol^-1 K^-1, what is ΔS°?
Respuesta
+80 J mol^-1 K^-1.
Tarjeta 446
Pregunta
How do electrode masses change in a Zn–Cu galvanic cell?
Respuesta
The Zn anode loses mass as Zn → Zn²⁺ + 2e⁻, while the Cu cathode gains mass as Cu²⁺ + 2e⁻ → Cu.
Tarjeta 447
Pregunta
What is ΔG° when ΔH° = 50 kJ mol^-1, ΔS° = 0.200 kJ mol^-1 K^-1, and T = 300 K?
Respuesta
-10 kJ mol^-1, from ΔG° = 50 − (300)(0.200).
Tarjeta 448
Pregunta
Why can temperature change a solid's solubility?
Respuesta
Temperature changes the balance of ΔH and TΔS, so it changes the free energy of dissolution and the equilibrium constant.
Tarjeta 449
Pregunta
What does the size of ΔG° relative to RT imply about K?
Respuesta
ΔG° near zero gives K near 1. When |ΔG°| is much larger than RT, K is far from 1: negative ΔG° gives K ≫ 1, while positive ΔG° gives K ≪ 1.
Tarjeta 450
Pregunta
Bubbles form at an inert cathode in acidic solution; which half-reaction can explain them?
Respuesta
2H⁺ + 2e⁻ → H₂(g). Gas evolution at the cathode can be direct evidence of reduction.
450 tarjetas
Advanced High School Chemistry Flashcards: Complete 9-Part Course Review
Flashcards se abrirá para que puedas empezar a estudiar.