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