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