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