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