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.
دربارهٔ این دسته
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.
کارتهای این دسته
کارت ۱
پرسش
What does one mole count?
پاسخ
Exactly 6.02214076 × 10^23 representative particles.
کارت ۲
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What does a peak in an element's mass spectrum represent?
پاسخ
An isotope with a particular mass-to-charge ratio; for singly charged monatomic ions, the position tracks isotopic mass.
کارت ۳
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What does an empirical formula show?
پاسخ
The lowest whole-number ratio of the elements' atoms in a compound.
کارت ۴
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How does a mixture differ from a pure substance at the particle level?
پاسخ
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.
کارت ۵
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Which particles make up an atom's nucleus?
پاسخ
Protons and neutrons. Electrons occupy the space outside the nucleus.
کارت ۶
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What does a larger binding energy on a PES spectrum mean?
پاسخ
More energy is required to remove that electron, so it is held more strongly by the nucleus.
کارت ۷
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How does atomic radius generally change across a period and down a group?
پاسخ
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.
کارت ۸
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What typical ion charge do Group 1 metals form?
پاسخ
+1, by losing their one valence electron.
کارت ۹
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How do you convert moles to particles?
پاسخ
Multiply by Avogadro's number: particles = moles × 6.022 × 10^23 mol^-1.
کارت ۱۰
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How is average atomic mass estimated from isotope data?
پاسخ
Add each isotopic mass multiplied by its fractional abundance.
کارت ۱۱
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How is an element's mass percent in a compound calculated?
پاسخ
Divide the mass contributed by that element by the compound's molar mass, then multiply by 100%.
کارت ۱۲
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How can measured elemental composition reveal a sample's purity?
پاسخ
Compare the measured mass fraction with the fraction expected for the pure compound; a mismatch indicates another component.
کارت ۱۳
پرسش
How do you build a ground-state electron configuration with the Aufbau principle?
پاسخ
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.
کارت ۱۴
پرسش
What does the relative area or height of an ideal PES peak indicate?
پاسخ
The relative number of electrons in the corresponding subshell.
کارت ۱۵
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How does first ionization energy generally change across a period and down a group?
پاسخ
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.
کارت ۱۶
پرسش
Why do elements in the same group form similar compounds?
پاسخ
Their ground-state valence patterns repeat, including which outer subshells are full or partly full. That leads to similar bonding and typical ion charges.
کارت ۱۷
پرسش
How do you convert a sample's mass to moles?
پاسخ
Divide its mass by its molar mass: n = m/M.
کارت ۱۸
پرسش
Which mass-spectrum interpretation lies outside the usual single-element model used in this deck?
پاسخ
Assigning peaks in mixtures or peaks from multiply charged or polyatomic species; the standard model uses singly charged monatomic ions of one element.
کارت ۱۹
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What does the law of definite proportions state?
پاسخ
Every pure sample of a given compound has the same element mass ratios.
کارت ۲۰
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Why can two samples of the same mixture have different compositions?
پاسخ
Mixture components are physically combined, so their relative amounts are not fixed by a chemical formula.
کارت ۲۱
پرسش
How does Coulomb's law connect charge and separation to attraction?
پاسخ
Attraction grows with the magnitude of the charge product and decreases with the square of the separation distance.
کارت ۲۲
پرسش
Which PES electrons usually appear at the highest binding energy?
پاسخ
Core electrons closest to the nucleus, because they feel the strongest nuclear attraction.
کارت ۲۳
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How does electron affinity generally change across a period and down a group?
پاسخ
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.
کارت ۲۴
پرسش
Why are alkali metals generally more reactive down the group?
پاسخ
Their valence electron is farther from the nucleus and easier to remove.
کارت ۲۵
پرسش
How many moles are in 18.0 g of H₂O?
پاسخ
About 0.999 mol. Use 18.0 g ÷ 18.02 g mol^-1.
کارت ۲۶
پرسش
An element is 75% isotope 10 and 25% isotope 11; what is its average atomic mass?
پاسخ
10.25 u. Calculate (0.75 × 10) + (0.25 × 11).
کارت ۲۷
پرسش
A compound is 40.0% C, 6.7% H, and 53.3% O by mass; what is its empirical formula?
پاسخ
CH₂O. For a 100 g sample, convert each mass to moles and divide by the smallest amount.
کارت ۲۸
پرسش
A 10.0 g impure sample contains 8.5 g of the target compound; what is its mass-percent purity?
پاسخ
85%. Calculate (8.5 g ÷ 10.0 g) × 100%.
کارت ۲۹
پرسش
Which electrons are removed first when a transition metal forms a cation?
پاسخ
Electrons in the occupied orbital with the highest principal quantum number: 4s before 3d. For example, Fe²⁺ is [Ar] 3d⁶.
کارت ۳۰
پرسش
A PES spectrum has peaks proportional to 2, 2, and 6 electrons; which configuration fits?
پاسخ
1s² 2s² 2p⁶, the configuration of Ne.
کارت ۳۱
پرسش
How does electronegativity generally change across a period and down a group?
پاسخ
It increases from left to right across a period and decreases down a group as atomic size and shielding increase.
کارت ۳۲
پرسش
What empirical formula results from Al³⁺ and O²⁻?
پاسخ
Al₂O₃, because two Al³⁺ ions balance three O²⁻ ions.
کارت ۳۳
پرسش
How does a particle's mass in atomic mass units relate to its molar mass?
پاسخ
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.
کارت ۳۴
پرسش
What does the tallest isotope peak usually indicate in a simple mass spectrum?
پاسخ
The most abundant isotope, assuming comparable detection response and singly charged ions.
کارت ۳۵
پرسش
How much oxygen is present in 25.0 g of a compound that is 32.0% oxygen by mass?
پاسخ
8.00 g O. Multiply 25.0 g by 0.320.
کارت ۳۶
پرسش
What does a particle diagram with two unbonded species in changing ratios represent?
پاسخ
A mixture, because more than one particle type is present and the ratio is not fixed in a formula unit.
کارت ۳۷
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What distinguishes valence electrons from core electrons?
پاسخ
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.
کارت ۳۸
پرسش
Why can PES peak groups reveal an atom's occupied subshells?
پاسخ
Electrons in different subshells require distinct removal energies, producing separate binding-energy groups.
کارت ۳۹
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How do ion radii compare with neutral atoms and within an isoelectronic series?
پاسخ
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.
کارت ۴۰
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What formula is expected for a compound between a Group 2 metal M and a Group 17 nonmetal X?
پاسخ
MX₂, because M forms M²⁺ and X forms X⁻.
کارت ۴۱
پرسش
When is a covalent bond considered nonpolar?
پاسخ
When the bonded atoms have identical or very similar electronegativities, so the shared electron density is distributed approximately evenly.
کارت ۴۲
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Why does a bonded pair of atoms have an equilibrium bond length?
پاسخ
At that separation, attractive and repulsive interactions balance at minimum potential energy.
کارت ۴۳
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How are particles arranged in an ionic solid?
پاسخ
Cations and anions occupy a repeating three-dimensional lattice held by electrostatic attraction.
کارت ۴۴
پرسش
What model explains bonding in a metal?
پاسخ
Positive metal cores are held together by attraction to mobile, delocalized valence electrons.
کارت ۴۵
پرسش
How do you construct a Lewis diagram?
پاسخ
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.
کارت ۴۶
پرسش
What does resonance mean in a molecule or ion?
پاسخ
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.
کارت ۴۷
پرسش
What determines molecular shape in VSEPR theory?
پاسخ
Electron domains around the central atom arrange to minimize repulsions.
کارت ۴۸
پرسش
How does an ionic bond differ from a covalent bond?
پاسخ
Ionic bonding is attraction among oppositely charged ions in an extended structure; covalent bonding uses shared electron density between atoms.
کارت ۴۹
پرسش
What happens to potential energy when bonded atoms are pushed much closer than equilibrium?
پاسخ
Potential energy rises sharply because nucleus–nucleus and electron–electron repulsions dominate.
کارت ۵۰
پرسش
Why are many ionic solids brittle?
پاسخ
A shifted lattice can align like charges, creating strong repulsion that splits the crystal.
کارت ۵۱
پرسش
What molecular shapes arise from two electron domains with no lone pairs and from three domains with zero or one lone pair?
پاسخ
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°.
کارت ۵۲
پرسش
Why are metals electrically conductive as solids?
پاسخ
Their delocalized electrons can move through the solid when an electric field is applied.
کارت ۵۳
پرسش
How is formal charge calculated for an atom in a Lewis diagram?
پاسخ
Formal charge = valence electrons − nonbonding electrons − half the bonding electrons.
کارت ۵۴
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Why can't electronegativity difference alone classify a bond as ionic or covalent?
پاسخ
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.
کارت ۵۵
پرسش
Which shapes and bond-angle trends arise as lone pairs replace bonds in four electron domains?
پاسخ
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.
کارت ۵۶
پرسش
What feature of a potential-energy curve represents bond dissociation energy?
پاسخ
The energy difference from the curve's minimum to the separated-atoms limit.
کارت ۵۷
پرسش
When does an ionic compound conduct electricity?
پاسخ
When molten or dissolved so its ions can move; not as a rigid solid lattice.
کارت ۵۸
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What is a substitutional alloy?
پاسخ
An alloy in which atoms of a similar size replace some host-metal atoms in the lattice.
کارت ۵۹
پرسش
How do two, three, and four electron domains map to hybridization?
پاسخ
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.
کارت ۶۰
پرسش
What usually makes one resonance contributor more favorable than another?
پاسخ
Smaller formal-charge magnitudes, appropriate negative charge on more electronegative atoms, and complete valence shells where applicable.
کارت ۶۱
پرسش
How many sigma and pi bonds are in single, double, and triple bonds?
پاسخ
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.
کارت ۶۲
پرسش
Why is a polar covalent bond polar?
پاسخ
Unequal electronegativity creates an uneven sharing of electron density and partial charges.
کارت ۶۳
پرسش
Which molecular shapes arise as lone pairs replace bonds in five electron domains?
پاسخ
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.
کارت ۶۴
پرسش
How do ionic charge and ionic radius affect attraction between ions?
پاسخ
Larger charge magnitudes and smaller ionic radii produce stronger attraction because the charge product increases and the ion centers are closer.
کارت ۶۵
پرسش
Why do ionic solids often have high melting points?
پاسخ
Many strong Coulombic attractions throughout the lattice must be overcome to free the ions.
کارت ۶۶
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What is an interstitial alloy?
پاسخ
A smaller atom occupies holes between host-metal atoms, often making lattice layers harder to slide.
کارت ۶۷
پرسش
What shape has six bonding domains and no lone pairs on the central atom?
پاسخ
Octahedral.
کارت ۶۸
پرسش
Which elements commonly form incomplete octets in stable Lewis diagrams?
پاسخ
Hydrogen forms a duet, and electron-deficient central atoms such as boron or beryllium can have fewer than eight electrons.
کارت ۶۹
پرسش
How do bond order and atomic size affect covalent bond length and strength?
پاسخ
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.
کارت ۷۰
پرسش
What bonding model best fits a sample that is malleable and conducts as a solid?
پاسخ
Metallic bonding with mobile, delocalized electrons and nondirectional attractions.
کارت ۷۱
پرسش
What shape has six electron domains, five bonds, and one lone pair?
پاسخ
Square pyramidal.
کارت ۷۲
پرسش
Which lattice should have stronger attractions: MgO or NaCl, assuming similar separations?
پاسخ
MgO, because the charge product for Mg²⁺ and O²⁻ is larger than for Na⁺ and Cl⁻.
کارت ۷۳
پرسش
Why are pure metals often malleable?
پاسخ
Metal cores can shift while the mobile electron sea maintains nondirectional attraction instead of exposing fixed like-charge planes.
کارت ۷۴
پرسش
What is the best Lewis structure for CO₂?
پاسخ
O=C=O, with two lone pairs on each oxygen and no formal charges.
کارت ۷۵
پرسش
What shape has six electron domains, four bonds, and two opposite lone pairs?
پاسخ
Square planar.
کارت ۷۶
پرسش
What limitation does an odd total number of valence electrons create for a Lewis diagram?
پاسخ
At least one electron must remain unpaired, so not every atom can have a complete paired-electron octet.
کارت ۷۷
پرسش
What does a higher bond order do to a bond's potential-energy curve?
پاسخ
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.
کارت ۷۸
پرسش
When can a carbon–carbon double bond produce geometric isomers?
پاسخ
When each carbon has two different substituents. The pi bond restricts rotation, so distinct spatial arrangements can persist.
کارت ۷۹
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When may a third-period central atom exceed an octet in a Lewis diagram?
پاسخ
When the valid electron count and lower formal charges favor an expanded valence shell, as in species such as SF₆.
کارت ۸۰
پرسش
How do you decide whether a molecule with polar bonds is polar overall?
پاسخ
Add the bond-dipole vectors using the molecular shape; symmetry may cancel them, while an asymmetric arrangement leaves a net dipole.
کارت ۸۱
پرسش
Which interparticle forces act between all atoms and molecules?
پاسخ
London dispersion forces, caused by temporary and induced dipoles.
کارت ۸۲
پرسش
What four broad solid types does this deck compare?
پاسخ
Ionic, metallic, molecular, and covalent-network solids.
کارت ۸۳
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How do gas particles differ from liquid particles?
پاسخ
Gas particles are much farther apart and move independently; liquid particles stay close but can move past one another.
کارت ۸۴
پرسش
What relationship connects pressure, volume, amount, and temperature for an ideal gas?
پاسخ
PV = nRT, with absolute temperature in kelvins and units consistent with R.
کارت ۸۵
پرسش
What does temperature measure in kinetic molecular theory?
پاسخ
The particles' average translational kinetic energy.
کارت ۸۶
پرسش
What two ideal-gas assumptions fail most clearly for real gases?
پاسخ
Particles have nonzero volume and experience intermolecular attractions.
کارت ۸۷
پرسش
How is molarity defined?
پاسخ
Moles of solute per liter of solution: M = n/V.
کارت ۸۸
پرسش
What must a correct particulate diagram of NaCl(aq) show?
پاسخ
Separated Na⁺ and Cl⁻ ions in a 1:1 ratio, each surrounded by oriented water molecules.
کارت ۸۹
پرسش
Which separation method removes an insoluble solid from a liquid?
پاسخ
Filtration: the solid stays as residue while the liquid passes as filtrate.
کارت ۹۰
پرسش
What does “like dissolves like” mean at the particle level?
پاسخ
A solute tends to dissolve when new solute–solvent attractions can compete with the attractions disrupted in the pure substances.
کارت ۹۱
پرسش
What happens when matter absorbs electromagnetic radiation?
پاسخ
Its particles move to an allowed higher-energy state when the photon energy matches the energy gap.
کارت ۹۲
پرسش
Which equations connect photon energy, frequency, and wavelength?
پاسخ
E = hν and c = λν.
کارت ۹۳
پرسش
What is the Beer–Lambert law?
پاسخ
A = εbc: absorbance equals molar absorptivity at the chosen wavelength times path length times concentration.
کارت ۹۴
پرسش
What molecular features generally strengthen London dispersion forces?
پاسخ
More electrons and a more polarizable cloud strengthen temporary dipoles; greater contact area and accessible π-electron density can also strengthen the attraction.
کارت ۹۵
پرسش
Why do molecular solids usually have low melting points and fail to conduct electricity?
پاسخ
Distinct molecules are held together by relatively weak intermolecular forces, while their valence electrons stay localized in bonds and lone pairs.
کارت ۹۶
پرسش
How do particles move in a solid?
پاسخ
They vibrate about fixed positions and do not translate past one another.
کارت ۹۷
پرسش
What graph shapes connect V or P with T(K) or n for an ideal gas?
پاسخ
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.
کارت ۹۸
پرسش
At the same temperature, which gas has the greater average molecular speed: He or Xe?
پاسخ
He. Both have the same average kinetic energy, but KE = ½mv² means the lower-mass particles move faster.
کارت ۹۹
پرسش
Why do real gases deviate more at high pressure?
پاسخ
Particles are crowded, so their own volume is no longer negligible compared with the container volume.
کارت ۱۰۰
پرسش
Which relationship describes dilution when solute amount is conserved?
پاسخ
M₁V₁ = M₂V₂.
کارت ۱۰۱
پرسش
Why does an aqueous ionic solution conduct electricity?
پاسخ
Dissolved ions are mobile and carry charge through the solution.
کارت ۱۰۲
پرسش
Which property lets simple distillation separate two liquids?
پاسخ
A sufficient difference in volatility or boiling point, so the vapor is enriched in the more volatile component.
کارت ۱۰۳
پرسش
Why are many ionic compounds soluble in water but poorly soluble in a nonpolar solvent?
پاسخ
Water can form strong ion–dipole attractions that stabilize separated ions; a nonpolar solvent cannot provide comparable attractions.
کارت ۱۰۴
پرسش
Which molecular transition is commonly associated with microwave absorption?
پاسخ
A transition between quantized rotational energy levels.
کارت ۱۰۵
پرسش
What frequency corresponds to a 600. nm photon?
پاسخ
5.00 × 10^14 s^-1. Use ν = c/λ with 600. nm = 6.00 × 10^-7 m.
کارت ۱۰۶
پرسش
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?
پاسخ
0.40. Use A = εbc.
کارت ۱۰۷
پرسش
What conditions allow hydrogen bonding between two molecules?
پاسخ
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.
کارت ۱۰۸
پرسش
Why are covalent-network solids often very hard with high melting points?
پاسخ
A continuous network of strong covalent bonds must be disrupted to deform or melt the solid.
کارت ۱۰۹
پرسش
Why do a substance's solid and liquid phases usually have similar molar volumes?
پاسخ
Their particles remain in close contact in both phases, even though liquid particles can move past one another.
کارت ۱۱۰
پرسش
How is a gas mixture's total pressure related to its component pressures?
پاسخ
Ptotal = ΣPi; each partial pressure is the pressure that component would exert alone in the same volume and temperature.
کارت ۱۱۱
پرسش
What microscopic events create gas pressure?
پاسخ
Gas particles collide with container walls and transfer momentum.
کارت ۱۱۲
پرسش
Why do intermolecular attractions matter more for gases at low temperature?
پاسخ
Particles move more slowly, so attractions can alter their paths and promote condensation.
کارت ۱۱۳
پرسش
What is the final concentration after 50.0 mL of 2.00 M solution is diluted to 200.0 mL?
پاسخ
0.500 M. Use M₂ = M₁V₁/V₂.
کارت ۱۱۴
پرسش
What must a particulate representation of a solution communicate?
پاسخ
The relative concentrations of its components and the particle-level interactions among those components.
کارت ۱۱۵
پرسش
What causes components to separate in chromatography?
پاسخ
They differ in attraction to the stationary phase and the mobile phase, so they travel at different rates.
کارت ۱۱۶
پرسش
Why are many polar molecular solutes soluble in water?
پاسخ
Dipole attractions or hydrogen bonds with water can replace the solute–solute and water–water attractions disrupted during mixing.
کارت ۱۱۷
پرسش
Why does an atom produce discrete spectral lines?
پاسخ
Its electrons can occupy only quantized energy levels, so only photons matching allowed energy differences are absorbed or emitted.
کارت ۱۱۸
پرسش
How does photon energy change when frequency doubles?
پاسخ
It doubles because E = hν.
کارت ۱۱۹
پرسش
Why is a calibration curve useful in spectrophotometry?
پاسخ
It relates measured absorbance to known concentrations, letting an unknown concentration be read by interpolation within the linear range.
کارت ۱۲۰
پرسش
How does an ion–dipole attraction form, and how does it compare with dipole–dipole attraction?
پاسخ
An ion attracts the oppositely charged end of a polar molecule. Ion–dipole attractions tend to be stronger than dipole–dipole attractions.
کارت ۱۲۱
پرسش
Which solid type is usually both conductive and malleable?
پاسخ
A metallic solid, because its delocalized electrons move and its nondirectional bonding tolerates layer shifts.
کارت ۱۲۲
پرسش
How does a crystalline solid differ from an amorphous solid?
پاسخ
A crystalline solid has long-range repeating order; an amorphous solid lacks that long-range periodic arrangement.
کارت ۱۲۳
پرسش
How is a gas component's partial pressure found from mole fraction?
پاسخ
Pi = XiPtotal.
کارت ۱۲۴
پرسش
How does heating a fixed-volume gas affect its pressure in the ideal model?
پاسخ
Pressure rises because faster particles collide with the walls more forcefully and frequently.
کارت ۱۲۵
پرسش
Why can attractions make a real gas's measured pressure lower than the ideal prediction?
پاسخ
Attractions pull approaching particles away from the walls, reducing momentum transfer during wall collisions.
کارت ۱۲۶
پرسش
How many moles of ions result from complete dissolution of 0.20 mol CaCl₂?
پاسخ
0.60 mol ions: 0.20 mol Ca²⁺ plus 0.40 mol Cl⁻.
کارت ۱۲۷
پرسش
How should water orient around Cl⁻ in a particle model?
پاسخ
Its partially positive hydrogen ends point toward Cl⁻.
کارت ۱۲۸
پرسش
Can filtration separate dissolved components of a liquid solution?
پاسخ
No. Dissolved particles pass through the filter with the solvent; filtration only retains an insoluble solid.
کارت ۱۲۹
پرسش
Why do nonpolar molecular solutes often dissolve in nonpolar solvents?
پاسخ
Both rely mainly on compatible London dispersion forces, so mixing can replace the attractions disrupted in the separate substances.
کارت ۱۳۰
پرسش
What does a shorter absorbed wavelength imply about an energy transition?
پاسخ
A larger energy gap because E = hc/λ.
کارت ۱۳۱
پرسش
What is the energy of a photon with frequency 5.0 × 10^14 s^-1?
پاسخ
3.3 × 10^-19 J. Multiply by Planck's constant: E = (6.626 × 10^-34 J·s)(5.0 × 10^14 s^-1).
کارت ۱۳۲
پرسش
How does doubling cuvette path length affect absorbance in the linear Beer–Lambert range?
پاسخ
Absorbance doubles if concentration and molar absorptivity stay constant.
کارت ۱۳۳
پرسش
How can noncovalent interactions affect a large biomolecule?
پاسخ
Attractions between molecules or between different regions of the same molecule help set its shape, which strongly affects its properties and function.
کارت ۱۳۴
پرسش
Why does an ionic solid usually fail to conduct as a solid?
پاسخ
Its ions are fixed in lattice positions. The same substance conducts when molten or dissolved because the ions can then move.
کارت ۱۳۵
پرسش
Why does a gas have no definite shape or volume?
پاسخ
Its widely spaced particles move constantly and experience minimal interparticle attraction, so they spread through the available container.
کارت ۱۳۶
پرسش
What graph shapes show the inverse pressure–volume relationship for a fixed amount of ideal gas at constant temperature?
پاسخ
A plot of P against V is a decreasing curve, while P against 1/V is a straight line through the origin.
کارت ۱۳۷
پرسش
At the same temperature, do different ideal gases have different average kinetic energies?
پاسخ
No. Average translational kinetic energy depends only on absolute temperature.
کارت ۱۳۸
پرسش
Under which conditions is ideal-gas behavior most accurate?
پاسخ
Low pressure and high temperature, where particles are far apart and attractions matter least.
کارت ۱۳۹
پرسش
What particle-level feature distinguishes a solution from a heterogeneous mixture?
پاسخ
A solution—whether solid, liquid, or gas—is uniform throughout; a heterogeneous mixture has regions or phases with different compositions.
کارت ۱۴۰
پرسش
How should water orient around Na⁺ in a particulate model?
پاسخ
Its partially negative oxygen end points toward Na⁺.
کارت ۱۴۱
پرسش
In paper chromatography, why does one solute spot travel farther than another?
پاسخ
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.
کارت ۱۴۲
پرسش
What energy competition helps explain whether an ionic solid dissolves?
پاسخ
The energy needed to separate lattice ions competes with the energy released when ion–solvent attractions form.
کارت ۱۴۳
پرسش
Which molecular motions commonly absorb infrared radiation?
پاسخ
Bond vibrations whose changing dipole can interact with the radiation.
کارت ۱۴۴
پرسش
Why must wavelength be converted to meters in c = λν when c is in m s^-1?
پاسخ
Consistent units are required so meters cancel correctly and frequency comes out in s^-1.
کارت ۱۴۵
پرسش
How can fingerprints on a cuvette affect a visible-light absorbance reading?
پاسخ
They can absorb or scatter extra light, making measured absorbance too high and the inferred concentration too high.
کارت ۱۴۶
پرسش
What causes and controls the strength of dipole–dipole attractions?
پاسخ
Opposite partial charges on neighboring polar molecules attract. Strength increases with larger molecular dipoles and depends on how favorably the dipoles are oriented.
کارت ۱۴۷
پرسش
Why is graphite conductive and soft while diamond is insulating and hard?
پاسخ
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.
کارت ۱۴۸
پرسش
Why are gases much more compressible than liquids?
پاسخ
Gas particles have large empty spaces between them; liquid particles are already close together.
کارت ۱۴۹
پرسش
What volume does 0.500 mol CO₂ occupy at 1.00 atm and 300. K if it behaves ideally?
پاسخ
12.3 L. Use V = nRT/P = (0.500 mol)(0.08206 L atm mol^-1 K^-1)(300. K)/(1.00 atm).
کارت ۱۵۰
پرسش
Why does a lighter gas effuse faster than a heavier gas at the same temperature?
پاسخ
Its particles have a higher average speed because equal average kinetic energy is shared by less mass.
کارت ۱۵۱
پرسش
How does finite particle volume affect a real gas at very high pressure?
پاسخ
The free volume available for particle motion is smaller than the container volume assumed by the ideal model.
کارت ۱۵۲
پرسش
How should 250.0 mL of 0.100 M NaCl be prepared from solid NaCl?
پاسخ
Dissolve 0.0250 mol NaCl, or 1.46 g, then dilute to exactly 250.0 mL in a volumetric flask.
کارت ۱۵۳
پرسش
What changes in a particle diagram when a solution is diluted without losing solute?
پاسخ
The solute-particle count stays constant while solvent volume and particle spacing increase.
کارت ۱۵۴
پرسش
Why is fractional distillation better than simple distillation for liquids with close boiling points?
پاسخ
Repeated vaporization–condensation steps enrich the vapor in the more volatile component more effectively.
کارت ۱۵۵
پرسش
Why are oil and water usually immiscible?
پاسخ
Water's strong hydrogen-bond network isn't replaced by equally strong water–oil attractions, so the substances separate into phases.
کارت ۱۵۶
پرسش
Which molecular transition is commonly associated with ultraviolet or visible absorption?
پاسخ
A transition between electronic energy levels.
کارت ۱۵۷
پرسش
Which photon carries more energy, blue light or red light?
پاسخ
Blue light, because it has shorter wavelength and higher frequency.
کارت ۱۵۸
پرسش
Why is absorbance often measured at the wavelength of maximum absorbance in Beer–Lambert analysis?
پاسخ
It gives the largest concentration-sensitive signal, and the flat top near the maximum makes small wavelength-setting errors less influential.
کارت ۱۵۹
پرسش
What creates a dipole–induced-dipole attraction, and what controls its strength?
پاسخ
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.
کارت ۱۶۰
پرسش
How do stronger intermolecular forces affect vapor pressure, boiling point, and melting point?
پاسخ
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.
کارت ۱۶۱
پرسش
How do particles behave in a liquid?
پاسخ
They stay in close contact while moving and colliding continuously. Temperature and interparticle attractions affect their arrangement and motion.
کارت ۱۶۲
پرسش
Why must Celsius temperature be converted to kelvins in gas-law calculations?
پاسخ
Gas-law proportionalities require an absolute temperature scale whose zero corresponds to zero extrapolated thermal motion.
کارت ۱۶۳
پرسش
How does raising temperature change a Maxwell–Boltzmann speed distribution?
پاسخ
The distribution broadens, its peak lowers and shifts right, and a larger fraction of particles have high speed.
کارت ۱۶۴
پرسش
Why does the ideal-gas model treat collisions as elastic?
پاسخ
It assumes total kinetic energy is conserved in particle–particle and particle–wall collisions.
کارت ۱۶۵
پرسش
How many moles of solute are in 75.0 mL of a 0.400 M solution?
پاسخ
0.0300 mol. Multiply 0.400 mol L^-1 by 0.0750 L.
کارت ۱۶۶
پرسش
For equal solution volumes drawn at the same scale, what shows which solution is more concentrated?
پاسخ
The more concentrated diagram contains more solute particles in that equal volume.
کارت ۱۶۷
پرسش
How do differences in intermolecular attractions let distillation separate a liquid solution?
پاسخ
They give the components different vapor pressures, so the vapor is enriched in the more volatile component.
کارت ۱۶۸
پرسش
What comparison helps predict whether two liquids will be miscible?
پاسخ
Liquids with similar types and strengths of intermolecular attractions are more likely to mix uniformly.
کارت ۱۶۹
پرسش
How can an absorption spectrum help identify a substance?
پاسخ
Its allowed energy gaps produce a characteristic pattern of absorbed wavelengths that can be compared with known spectra.
کارت ۱۷۰
پرسش
How does absorbing or emitting a photon change an atom's or molecule's energy?
پاسخ
Absorption raises the species' energy by exactly the photon energy; emission lowers it by the same amount.
کارت ۱۷۱
پرسش
What macroscopic evidence can support that a chemical reaction occurred?
پاسخ
Evidence can include gas formation, precipitate formation, a persistent color change, or an energy change, interpreted with particle-level changes.
کارت ۱۷۲
پرسش
What does a net ionic equation include?
پاسخ
Only the dissolved or reacting species that undergo chemical change; spectator ions are omitted.
کارت ۱۷۳
پرسش
What must a correct particulate reaction diagram conserve?
پاسخ
The number of atoms of every element and the total charge.
کارت ۱۷۴
پرسش
What distinguishes a chemical change from a physical change?
پاسخ
A chemical change rearranges bonds into new substances; a physical change alters state or arrangement without changing chemical identity.
کارت ۱۷۵
پرسش
What does a balanced equation's coefficient ratio provide?
پاسخ
The mole ratio among reacting and produced species.
کارت ۱۷۶
پرسش
What is the equivalence point of a titration?
پاسخ
The point where titrant and analyte have reacted in the stoichiometric ratio given by the balanced equation.
کارت ۱۷۷
پرسش
What defines a precipitation reaction?
پاسخ
Aqueous ions combine to form a sparingly soluble solid.
کارت ۱۷۸
پرسش
What happens in a Brønsted–Lowry acid–base reaction?
پاسخ
A proton transfers from the acid (donor) to the base (acceptor). In aqueous solution, H₂O can play either role.
کارت ۱۷۹
پرسش
What does oxidation mean in a redox reaction?
پاسخ
Loss of electrons and an increase in oxidation number.
کارت ۱۸۰
پرسش
What particle-level change confirms that a process is chemical?
پاسخ
Atoms rearrange into new combinations, producing substances with different compositions.
کارت ۱۸۱
پرسش
Which ions are spectators when AgNO₃(aq) reacts with NaCl(aq)?
پاسخ
Na⁺ and NO₃⁻. The net ionic reaction is Ag⁺(aq) + Cl⁻(aq) → AgCl(s).
کارت ۱۸۲
پرسش
How does a particulate diagram reveal the limiting reactant?
پاسخ
After forming the maximum product allowed by the ratio, none of the limiting reactant remains while excess reactant particles do.
کارت ۱۸۳
پرسش
Is melting ice a chemical or physical change?
پاسخ
A physical change. H₂O molecules remain H₂O while their arrangement and motion change.
کارت ۱۸۴
پرسش
How is the limiting reactant identified from given amounts?
پاسخ
Convert each reactant to the same product amount using the balanced equation; the smaller product amount identifies the limiting reactant.
کارت ۱۸۵
پرسش
How does an endpoint differ from an equivalence point?
پاسخ
The endpoint is an observed signal such as indicator color change; the equivalence point is the exact stoichiometric condition.
کارت ۱۸۶
پرسش
How is complete combustion of a hydrocarbon in excess oxygen classified, and what products form?
پاسخ
It is a redox combustion reaction that forms CO₂ and H₂O.
کارت ۱۸۷
پرسش
What are the conjugate acid and conjugate base in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
پاسخ
NH₄⁺ is the conjugate acid of NH₃, and OH⁻ is the conjugate base of H₂O.
کارت ۱۸۸
پرسش
What does reduction mean in a redox reaction?
پاسخ
Gain of electrons and a decrease in oxidation number.
کارت ۱۸۹
پرسش
Which common changes are physical rather than chemical?
پاسخ
Phase changes and the formation or separation of mixtures are physical when each substance keeps its composition.
کارت ۱۹۰
پرسش
How are strong soluble electrolytes written in a complete ionic equation?
پاسخ
As separated aqueous ions; solids, liquids, gases, and weak electrolytes stay intact.
کارت ۱۹۱
پرسش
A diagram starts with six A particles and four B₂ particles for 2A + B₂ → 2AB; what remains after completion?
پاسخ
One B₂ remains. Six A consume three B₂ and form six AB.
کارت ۱۹۲
پرسش
Why is dissolving NaCl in water normally classified as a physical change?
پاسخ
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.
کارت ۱۹۳
پرسش
What mass of AgCl can form from 25.0 mL of 0.200 M AgNO₃ mixed with excess Cl⁻?
پاسخ
0.717 g AgCl. The 1:1 reaction gives 0.00500 mol AgCl; multiply by 143.32 g mol^-1.
کارت ۱۹۴
پرسش
What calculation finds unknown analyte moles at equivalence?
پاسخ
Use titrant moles, n = MV, then apply the balanced-reaction mole ratio.
کارت ۱۹۵
پرسش
Which feature identifies an acid–base, redox, or precipitation reaction?
پاسخ
Acid–base reactions transfer protons, redox reactions change oxidation numbers through electron transfer, and precipitation reactions form a sparingly soluble solid.
کارت ۱۹۶
پرسش
What is the net ionic equation for strong acid–strong base neutralization?
پاسخ
H⁺(aq) + OH⁻(aq) → H₂O(l).
کارت ۱۹۷
پرسش
What is the oxidation number of sulfur in SO₄²⁻?
پاسخ
+6. Four oxygens contribute -8 total, so sulfur must be +6 to give -2 overall.
کارت ۱۹۸
پرسش
Why can gas bubbles alone be ambiguous evidence of reaction?
پاسخ
Bubbles may also come from boiling or dissolved gas escaping, so the context and particle identities must support a chemical change.
کارت ۱۹۹
پرسش
How is melting ice represented as a balanced physical-change equation?
پاسخ
H₂O(s) → H₂O(l). The formula and atom count stay the same because only the physical state changes.
کارت ۲۰۰
پرسش
What does a particle diagram show when no reaction occurs after two aqueous ionic solutions mix?
پاسخ
All ions remain separated and solvated, with no new bonded particles, precipitate, or gas.
کارت ۲۰۱
پرسش
Why is rusting iron a chemical change?
پاسخ
Iron atoms form new iron-oxide substances through electron transfer and new bonding.
کارت ۲۰۲
پرسش
For 2H₂O₂(aq) → 2H₂O(l) + O₂(g), what volume of O₂ forms from 0.100 mol H₂O₂ at 298 K and 1.00 atm?
پاسخ
1.22 L O₂. The mole ratio gives 0.0500 mol O₂, then V = nRT/P.
کارت ۲۰۳
پرسش
A 25.0 mL monoprotic acid sample requires 20.0 mL of 0.150 M NaOH; what is the acid concentration?
پاسخ
0.120 M. At 1:1 equivalence, moles acid = 0.0200 L × 0.150 M, then divide by 0.0250 L.
کارت ۲۰۴
پرسش
Which salts does the minimum solubility rule in this deck treat as soluble?
پاسخ
All salts containing Na⁺, K⁺, NH₄⁺, or NO₃⁻ are treated as soluble in water.
کارت ۲۰۵
پرسش
How are the strengths of a conjugate acid and its conjugate base related?
پاسخ
A stronger acid has a weaker conjugate base, and a stronger base has a weaker conjugate acid.
کارت ۲۰۶
پرسش
How are oxidation and reduction half-reactions combined into one balanced equation?
پاسخ
Multiply them so electrons lost equal electrons gained, add the half-reactions, then cancel electrons and any identical species on both sides.
کارت ۲۰۷
پرسش
How do molecular, complete ionic, and net ionic equations differ?
پاسخ
Molecular equations keep compounds intact, complete ionic equations split strong soluble electrolytes, and net ionic equations remove spectators. All three conserve atoms and charge.
کارت ۲۰۸
پرسش
How should coefficients change particle counts in a reaction diagram?
پاسخ
They set whole-particle ratios while preserving each particle's chemical formula.
کارت ۲۰۹
پرسش
Is separating a mixture by distillation a chemical or physical change?
پاسخ
A physical change. Components change phase and location but keep their chemical identities.
کارت ۲۱۰
پرسش
What equation results from Cu → Cu²⁺ + 2e⁻ and Ag⁺ + e⁻ → Ag?
پاسخ
Cu + 2Ag⁺ → Cu²⁺ + 2Ag. Multiply the silver half-reaction by 2 and cancel 2e⁻; both atom counts and net charge then match.
کارت ۲۱۱
پرسش
How is average reaction rate found from a reactant concentration?
پاسخ
Use the negative concentration change divided by elapsed time, adjusted by its stoichiometric coefficient when comparing species rates.
کارت ۲۱۲
پرسش
What does a rate law express?
پاسخ
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.
کارت ۲۱۳
پرسش
A plot of ln[A] versus time is linear; what is the order in A and its integrated rate law?
پاسخ
First order: ln[A]t = ln[A]0 − kt, so the plot's slope is −k.
کارت ۲۱۴
پرسش
What is an elementary reaction?
پاسخ
A single step in a mechanism whose rate law follows directly from its reactant molecularity.
کارت ۲۱۵
پرسش
What two collision conditions are needed for reaction?
پاسخ
Sufficient collision energy and a productive molecular orientation.
کارت ۲۱۶
پرسش
What does activation energy represent on a reaction-energy profile?
پاسخ
The energy difference from the reactants to the transition state. The reaction coordinate tracks the step's structural progress, not elapsed time.
کارت ۲۱۷
پرسش
What must the elementary steps of a valid mechanism do when added?
پاسخ
Cancel intermediates and reproduce the overall balanced reaction.
کارت ۲۱۸
پرسش
How is a proposed mechanism tested against kinetics?
پاسخ
Its derived rate law must agree with the experimentally measured rate law.
کارت ۲۱۹
پرسش
What does a pre-equilibrium approximation assume?
پاسخ
A fast reversible step reaches equilibrium before a later slow step consumes its intermediate.
کارت ۲۲۰
پرسش
What does each peak on a multistep energy profile represent?
پاسخ
A transition state for one elementary step.
کارت ۲۲۱
پرسش
How does a catalyst increase reaction rate?
پاسخ
It provides an alternate mechanism with a lower activation-energy pathway.
کارت ۲۲۲
پرسش
Why does crushing a solid reactant usually increase its reaction rate?
پاسخ
Crushing increases exposed surface area, so more reactant particles can collide with the other reactant each second.
کارت ۲۲۳
پرسش
How is reaction order found from initial-rate data?
پاسخ
Compare trials where one reactant concentration changes while the others stay constant, then match the rate factor to the concentration factor.
کارت ۲۲۴
پرسش
A plot of [A] versus time is linear; what is the order in A and its integrated rate law?
پاسخ
Zero order: [A]t = [A]0 − kt, so the plot's slope is −k.
کارت ۲۲۵
پرسش
What is the rate law for the elementary step 2A + B → products?
پاسخ
rate = k[A]²[B]. This inference is valid because the step is elementary.
۴۵۰ کارت
AP Chemistry Flashcards: Complete 9-Unit Course Review
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کارت ۲۲۶
پرسش
How does raising temperature change a Maxwell–Boltzmann energy distribution and reaction rate?
پاسخ
The distribution shifts and broadens toward higher energies, so a larger fraction of collisions exceeds the activation-energy threshold and can react.
کارت ۲۲۷
پرسش
How is ΔH read from a reaction-energy profile?
پاسخ
ΔH = energy of products − energy of reactants.
کارت ۲۲۸
پرسش
What is a reaction intermediate?
پاسخ
A species formed in one mechanism step and consumed in a later step, so it cancels from the overall equation.
کارت ۲۲۹
پرسش
Why can't overall reaction coefficients usually supply rate-law exponents?
پاسخ
The overall equation hides the mechanism; exponents come from experiment unless the reaction is a stated elementary step.
کارت ۲۳۰
پرسش
How does pre-equilibrium remove an intermediate from a rate law?
پاسخ
Use the fast-step equilibrium relation to express the intermediate concentration in terms of stable reactants.
کارت ۲۳۱
پرسش
What does each valley between peaks represent on a multistep profile?
پاسخ
A reaction intermediate.
کارت ۲۳۲
پرسش
Does a catalyst change ΔH or the equilibrium constant?
پاسخ
No. It changes the pathway and rates, not reactant/product energies or the equilibrium composition.
کارت ۲۳۳
پرسش
For 2A → B, how are disappearance of A and appearance of B related?
پاسخ
Reaction rate = -(1/2)Δ[A]/Δt = Δ[B]/Δt.
کارت ۲۳۴
پرسش
How do the units of k depend on a rate law's overall order?
پاسخ
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.
کارت ۲۳۵
پرسش
A plot of 1/[A] versus time is linear; what is the order in A and its integrated rate law?
پاسخ
Second order: 1/[A]t = 1/[A]0 + kt, so the plot's slope is +k.
کارت ۲۳۶
پرسش
What is molecularity?
پاسخ
The number of reacting particles in an elementary step, such as unimolecular or bimolecular.
کارت ۲۳۷
پرسش
How does raising temperature affect k in the qualitative Arrhenius model?
پاسخ
k increases, often sharply, because a larger fraction of collisions can reach the transition state. Arrhenius-equation calculations are outside this deck’s scope.
کارت ۲۳۸
پرسش
A reactant falls from 0.80 M to 0.50 M in 30. s; what is its average disappearance rate to two significant figures?
پاسخ
0.010 M s^-1. Use -(0.50 − 0.80) M ÷ 30. s.
کارت ۲۳۹
پرسش
How does a catalyst differ from an intermediate in a mechanism?
پاسخ
A catalyst is consumed early and regenerated later; an intermediate is formed early and consumed later.
کارت ۲۴۰
پرسش
For 2NO₂ → NO₃ + NO (slow), followed by NO₃ + CO → NO₂ + CO₂ (fast), what rate law is predicted?
پاسخ
rate = k[NO₂]². The first step is elementary and rate-limiting, so its molecularity sets the observed rate law.
کارت ۲۴۱
پرسش
On a multistep reaction-energy profile, which feature often identifies the rate-determining step?
پاسخ
The step with the largest activation barrier measured from its preceding valley to its peak.
کارت ۲۴۲
پرسش
If changing [B] leaves rate unchanged, what is the order in B?
پاسخ
Zero order, so [B]^0 = 1 in the measured rate law.
کارت ۲۴۳
پرسش
What mechanism changes can binding, acid–base, or surface catalysis introduce?
پاسخ
They can orient reactants, lower activation barriers, or create new bound, protonated, or deprotonated intermediates and elementary steps; the catalyst is regenerated.
کارت ۲۴۴
پرسش
What is special about a first-order reaction's half-life?
پاسخ
It is constant and independent of starting concentration: t1/2 = ln 2/k. Radioactive decay is a common first-order example.
کارت ۲۴۵
پرسش
Why is a termolecular elementary collision uncommon?
پاسخ
Three particles must collide simultaneously with suitable energy and orientation, which is much less probable than one- or two-particle events.
کارت ۲۴۶
پرسش
On a reaction-energy profile, how are reverse activation energy, forward activation energy, and ΔH related?
پاسخ
Ea,reverse = Ea,forward − ΔH. The reverse barrier is measured from products to the same transition state.
کارت ۲۴۷
پرسش
Why can correct orientation matter even above the activation energy?
پاسخ
The colliding reactive sites must align so old bonds can break and new bonds can form along the reaction pathway.
کارت ۲۴۸
پرسش
How does detecting a proposed reaction intermediate affect a mechanism claim?
پاسخ
It supports a mechanism that contains that intermediate, but it doesn't prove that mechanism is unique.
کارت ۲۴۹
پرسش
For 2NO ⇌ N₂O₂ (fast equilibrium), followed by N₂O₂ + O₂ → 2NO₂ (slow), what observed rate law results?
پاسخ
rate = kobs[NO]²[O₂]. Start with rate = k₂[N₂O₂][O₂], use [N₂O₂] = K[NO]² from the fast equilibrium, then substitute.
کارت ۲۵۰
پرسش
What does the highest point of a one-step energy profile represent?
پاسخ
The transition state, an unstable arrangement at the top of the activation barrier.
کارت ۲۵۱
پرسش
What sign does q have for an endothermic system?
پاسخ
Positive, because the system absorbs heat from the surroundings.
کارت ۲۵۲
پرسش
How does an exothermic reaction appear on an enthalpy diagram?
پاسخ
Products lie below reactants, so ΔH is negative.
کارت ۲۵۳
پرسش
What condition defines thermal equilibrium?
پاسخ
Objects in contact have the same temperature, so there is no net heat transfer.
کارت ۲۵۴
پرسش
What equations relate heat capacity and temperature change to heat transfer?
پاسخ
Use q = mcΔT with specific heat capacity, or q = nCₘΔT with molar heat capacity.
کارت ۲۵۵
پرسش
Why is temperature constant during a phase-change plateau?
پاسخ
Added or removed energy changes interparticle potential energy instead of average kinetic energy.
کارت ۲۵۶
پرسش
What does ΔHrxn describe?
پاسخ
The heat absorbed or released at constant pressure for the reaction exactly as written under the stated conditions.
کارت ۲۵۷
پرسش
How is reaction enthalpy estimated from average bond enthalpies?
پاسخ
ΔHrxn ≈ Σ(bonds broken) − Σ(bonds formed).
کارت ۲۵۸
پرسش
What is the standard enthalpy of formation of an element in its standard state?
پاسخ
Zero by definition.
کارت ۲۵۹
پرسش
In a Hess’s law calculation, how should a step change when the target needs twice its reverse?
پاسخ
Reverse the equation, double every coefficient, and multiply its ΔH by -2.
کارت ۲۶۰
پرسش
How can energy cross a system boundary during a process?
پاسخ
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.
کارت ۲۶۱
پرسش
How does an endothermic reaction appear on an enthalpy diagram?
پاسخ
Products lie above reactants, so ΔH is positive.
کارت ۲۶۲
پرسش
How are heat gained by a system and heat lost by its surroundings related in an isolated setup?
پاسخ
qsystem = -qsurroundings.
کارت ۲۶۳
پرسش
In coffee-cup calorimetry, how is reaction heat related to solution heat?
پاسخ
qrxn = -qsolution when calorimeter heat is negligible and pressure is constant.
کارت ۲۶۴
پرسش
What heat is required to melt n moles at the melting point?
پاسخ
q = nΔHfus.
کارت ۲۶۵
پرسش
How does reversing a reaction change ΔH?
پاسخ
It reverses the sign of ΔH.
کارت ۲۶۶
پرسش
Why is breaking a bond endothermic?
پاسخ
Energy must be supplied to separate atoms against their bonding attraction.
کارت ۲۶۷
پرسش
How is ΔH°rxn calculated from standard enthalpies of formation?
پاسخ
ΣνΔHf°(products) − ΣνΔHf°(reactants).
کارت ۲۶۸
پرسش
How does multiplying an equation by 3 affect its ΔH?
پاسخ
Multiply ΔH by 3 because enthalpy change scales with reaction amount.
کارت ۲۶۹
پرسش
Why can an exothermic dissolution warm the solution?
پاسخ
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.
کارت ۲۷۰
پرسش
Does an energy diagram's activation barrier determine ΔH?
پاسخ
No. ΔH depends on reactant and product energy levels, while the barrier controls kinetics.
کارت ۲۷۱
پرسش
Why does heat flow from a warmer object to a cooler object?
پاسخ
Energy transfers through collisions until their average kinetic energies, and therefore temperatures, equalize.
کارت ۲۷۲
پرسش
How much heat warms 100.0 g of water by 5.0°C?
پاسخ
2.1 kJ. Use q = (100.0 g)(4.184 J g^-1 °C^-1)(5.0°C).
کارت ۲۷۳
پرسش
How are the molar enthalpies of a phase change and its reverse related?
پاسخ
They have equal magnitudes and opposite signs, such as ΔHcond = -ΔHvap and ΔHfreeze = -ΔHfus.
کارت ۲۷۴
پرسش
How does doubling every coefficient in a thermochemical equation affect ΔH?
پاسخ
It doubles ΔH.
کارت ۲۷۵
پرسش
Why is forming a bond exothermic?
پاسخ
Atoms move to a lower-potential-energy bonded arrangement and release energy.
کارت ۲۷۶
پرسش
What formation equation defines ΔHf° for CO₂(g)?
پاسخ
C(s, graphite) + O₂(g) → CO₂(g), forming exactly one mole from elements in standard states.
کارت ۲۷۷
پرسش
What should happen to intermediate species when equations in a Hess’s law calculation are added?
پاسخ
They cancel, leaving the target overall reaction.
کارت ۲۷۸
پرسش
If the surroundings warm during a process, what is the likely sign of qsystem?
پاسخ
Negative; the system likely released heat to the surroundings.
کارت ۲۷۹
پرسش
For a profile with reactants at 40 kJ and products at 10 kJ, what is ΔH?
پاسخ
-30 kJ for the reaction as drawn.
کارت ۲۸۰
پرسش
Assuming no phase change, what determines the final temperature when two substances exchange heat in an insulated container?
پاسخ
Energy conservation: q_warm + q_cool = 0. Use each substance's mass, heat capacity, and initial temperature to solve for the common final temperature.
کارت ۲۸۱
پرسش
How would heat loss to the room affect an exothermic calorimetry result?
پاسخ
The observed temperature rise is too small, so the calculated magnitude of released heat is too low.
کارت ۲۸۲
پرسش
What heat expression covers warming a liquid without a phase change?
پاسخ
q = mcΔT, not nΔHphase.
کارت ۲۸۳
پرسش
If forming 1 mol of product has ΔH = -50 kJ mol^-1, what is q when 2 mol forms?
پاسخ
-100 kJ. Use q = nΔH = (2 mol)(-50 kJ mol^-1).
کارت ۲۸۴
پرسش
Breaking reactant bonds requires 500 kJ, and forming product bonds releases 650 kJ; what is the estimated ΔH?
پاسخ
-150 kJ, from 500 − 650.
کارت ۲۸۵
پرسش
For CO(g) + ½O₂(g) → CO₂(g), what is ΔH°rxn if ΔHf°[CO] = -110.5 and ΔHf°[CO₂] = -393.5 kJ mol^-1?
پاسخ
-283.0 kJ. Use -393.5 - [-110.5 + ½(0)], since ΔHf°[O₂(g)] = 0.
کارت ۲۸۶
پرسش
In a Hess’s law calculation, two valid steps have ΔH values +25 kJ and -60 kJ; what is the combined ΔH?
پاسخ
-35 kJ, provided the equations add to the target reaction.
کارت ۲۸۷
پرسش
Why is “bonds breaking releases energy” incorrect?
پاسخ
Bond breaking absorbs energy; the overall reaction releases energy only when forming new bonds releases more than breaking old bonds requires.
کارت ۲۸۸
پرسش
How would melting appear on an energy diagram?
پاسخ
The liquid lies above the solid, so ΔHfus is positive; the diagram represents a physical, endothermic change.
کارت ۲۸۹
پرسش
Can two objects at the same temperature exchange energy microscopically?
پاسخ
Yes, but their energy transfers balance, so there is no net heat flow.
کارت ۲۹۰
پرسش
Why must the calorimeter's heat capacity be included when it isn't negligible?
پاسخ
The apparatus can absorb or release heat, so include q_cal = C_calΔT in the energy balance: q_process + q_solution + q_cal = 0.
کارت ۲۹۱
پرسش
What makes chemical equilibrium dynamic?
پاسخ
Forward and reverse reactions continue at equal rates even though macroscopic concentrations stay constant.
کارت ۲۹۲
پرسش
For aA + bB ⇌ cC, what is the concentration-form expression for Q?
پاسخ
Q = [C]^c / ([A]^a[B]^b), using current rather than necessarily equilibrium concentrations.
کارت ۲۹۳
پرسش
What does K much greater than 1 indicate?
پاسخ
Products predominate at equilibrium, though K says nothing about reaction speed.
کارت ۲۹۴
پرسش
How does reversing a reaction change its equilibrium constant?
پاسخ
K becomes 1/K.
کارت ۲۹۵
پرسش
Can a reversible system reach equilibrium when it starts with only products?
پاسخ
Yes, if the reverse reaction is possible. The equilibrium composition depends on temperature, initial amounts, and volume or pressure.
کارت ۲۹۶
پرسش
How do Q and K predict reaction direction?
پاسخ
Q < K shifts forward, Q > K shifts reverse, and Q = K means equilibrium.
کارت ۲۹۷
پرسش
Which species are omitted from a heterogeneous equilibrium expression?
پاسخ
Pure solids and pure liquids because their activities are effectively constant.
کارت ۲۹۸
پرسش
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?
پاسخ
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.
کارت ۲۹۹
پرسش
What does a flat concentration-time graph mean at equilibrium?
پاسخ
Each concentration is constant, not necessarily equal to the others.
کارت ۳۰۰
پرسش
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?
پاسخ
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.
کارت ۳۰۱
پرسش
What can Ksp tell you about a salt's solubility, and when can two Ksp values be compared directly?
پاسخ
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.
کارت ۳۰۲
پرسش
What is the common-ion effect on solubility?
پاسخ
Adding an ion already in the dissolution equilibrium usually decreases the solid's molar solubility.
کارت ۳۰۳
پرسش
How does uniform dilution shift an aqueous equilibrium based on the stoichiometric powers in Q?
پاسخ
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.
کارت ۳۰۴
پرسش
What happens if a reversible reaction starts with reactants only?
پاسخ
The forward rate is initially largest; products form, the reverse rate grows, and the rates eventually become equal.
کارت ۳۰۵
پرسش
What is the purpose of an ICE table?
پاسخ
To organize initial, change, and equilibrium concentrations using reaction stoichiometry.
کارت ۳۰۶
پرسش
Can a reaction with a very large K be slow?
پاسخ
Yes. K describes thermodynamic equilibrium position, while rate depends on kinetics and activation energy.
کارت ۳۰۷
پرسش
What happens to Q immediately after product concentration increases?
پاسخ
Q increases; if it rises above K, the reaction shifts toward reactants.
کارت ۳۰۸
پرسش
How does multiplying every reaction coefficient by 2 affect K?
پاسخ
The new equilibrium constant is K².
کارت ۳۰۹
پرسش
For A ⇌ B, Kc = 4.0 and initially [A] = 1.0 M and [B] = 0, what are the equilibrium concentrations?
پاسخ
[A] = 0.20 M and [B] = 0.80 M. Let x form: Kc = x/(1.0 − x) = 4.0, so x = 0.80 M.
کارت ۳۱۰
پرسش
What macroscopic properties stay constant at equilibrium?
پاسخ
Properties such as concentration, color, and pressure remain constant when external conditions are fixed.
کارت ۳۱۱
پرسش
How does decreasing volume shift a gaseous equilibrium?
پاسخ
Toward the side with fewer moles of gas, if the two sides have different gaseous mole counts.
کارت ۳۱۲
پرسش
For N₂ + 3H₂ ⇌ 2NH₃, what is Kc?
پاسخ
Kc = [NH₃]² / ([N₂][H₂]³).
کارت ۳۱۳
پرسش
For CaF₂(s) ⇌ Ca²⁺ + 2F⁻, how is Ksp written in terms of molar solubility s in pure water?
پاسخ
Ksp = s(2s)² = 4s³ because [Ca²⁺] = s and [F⁻] = 2s.
کارت ۳۱۴
پرسش
What does K much less than 1 indicate?
پاسخ
Reactants predominate at equilibrium.
کارت ۳۱۵
پرسش
How does decreasing a dissolved product's concentration or a gaseous product's partial pressure affect equilibrium when other Q terms are initially unchanged?
پاسخ
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.
کارت ۳۱۶
پرسش
Does equilibrium mean the reaction has stopped?
پاسخ
No. Both directions continue, but equal rates produce no net macroscopic change.
کارت ۳۱۷
پرسش
Why does adding NaF reduce CaF₂ solubility?
پاسخ
The added F⁻ raises Qsp, shifting the dissolution equilibrium toward solid CaF₂.
کارت ۳۱۸
پرسش
For N₂ + 3H₂ ⇌ 2NH₃, what is Kp when P_N₂ = 0.50 atm, P_H₂ = 1.50 atm, and P_NH₃ = 0.25 atm?
پاسخ
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.
کارت ۳۱۹
پرسش
What happens to Q when a gaseous equilibrium mixture is compressed at constant temperature if products have fewer gas moles?
پاسخ
Q falls relative to K, so the reaction shifts toward products.
کارت ۳۲۰
پرسش
How do K and Q transform when a reaction is reversed, its coefficients are multiplied, or reactions are added?
پاسخ
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.
کارت ۳۲۱
پرسش
When is the small-x approximation acceptable?
پاسخ
When x is small relative to the initial concentration and the final result confirms the neglected change is suitably small.
کارت ۳۲۲
پرسش
What graph feature shows a disturbance followed by re-equilibration?
پاسخ
A sudden or gradual concentration change followed by new constant plateaus while rates return to equality.
کارت ۳۲۳
پرسش
If Q = 0.20 and K = 5.0, which direction is favored next?
پاسخ
Forward, because Q < K.
کارت ۳۲۴
پرسش
At equilibrium, are reactant and product concentrations equal?
پاسخ
Not necessarily. They are constant, while forward and reverse rates are equal.
کارت ۳۲۵
پرسش
CaF₂ has Ksp = 3.2 × 10^-11 in pure water; what is its molar solubility?
پاسخ
2.0 × 10^-4 M. If the molar solubility is s, then [Ca²⁺] = s, [F⁻] = 2s, and Ksp = 4s³.
کارت ۳۲۶
پرسش
For N₂ + 3H₂ ⇌ 2NH₃, how is Qp written?
پاسخ
Qp = (P_NH₃)²/[(P_N₂)(P_H₂)³], using the current partial pressures rather than necessarily equilibrium values.
کارت ۳۲۷
پرسش
How does heating shift an endothermic forward reaction?
پاسخ
Toward products, and K increases because temperature changes the equilibrium constant.
کارت ۳۲۸
پرسش
Why do both forward and reverse rates change as equilibrium is approached?
پاسخ
As reactant and product concentrations change, the collision frequencies for the two directions change until their rates match.
کارت ۳۲۹
پرسش
CaF₂ has Ksp = 3.2 × 10^-11. What is its molar solubility in 0.10 M NaF?
پاسخ
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.
کارت ۳۳۰
پرسش
What concentration data must be used to calculate Kc?
پاسخ
Equilibrium concentrations, each raised to its stoichiometric coefficient and excluding pure solids and liquids.
کارت ۳۳۱
پرسش
What is a Brønsted–Lowry acid?
پاسخ
A proton donor.
کارت ۳۳۲
پرسش
How is pH defined?
پاسخ
pH = -log[H₃O⁺].
کارت ۳۳۳
پرسش
What is Ka for HA + H₂O ⇌ H₃O⁺ + A⁻?
پاسخ
Ka = [H₃O⁺][A⁻]/[HA].
کارت ۳۳۴
پرسش
How does stabilizing a base affect its basicity and the strength of its conjugate acid?
پاسخ
It makes the base weaker and its conjugate acid stronger. A more stable base is less willing to accept H⁺.
کارت ۳۳۵
پرسش
What is a Brønsted–Lowry base?
پاسخ
A proton acceptor.
کارت ۳۳۶
پرسش
At 25°C, what are Kw and the relationship between pH and pOH?
پاسخ
Kw = [H₃O⁺][OH⁻] = 1.0 × 10^-14. Taking negative logarithms gives pH + pOH = 14.00.
کارت ۳۳۷
پرسش
What is Kb for B + H₂O ⇌ BH⁺ + OH⁻?
پاسخ
Kb = [BH⁺][OH⁻]/[B].
کارت ۳۳۸
پرسش
Why can lowering pH increase the solubility of a salt containing a basic anion?
پاسخ
H₃O⁺ consumes the anion, pulling the dissolution equilibrium toward more dissolved ions.
کارت ۳۳۹
پرسش
What are conjugate acid–base pairs?
پاسخ
Species that differ by exactly one proton.
کارت ۳۴۰
پرسش
What is the pH of 1.0 × 10^-3 M HCl?
پاسخ
3.00, assuming complete dissociation and negligible water contribution.
کارت ۳۴۱
پرسش
How are pKa and pKb defined?
پاسخ
pKa = -log Ka, and pKb = -log Kb.
کارت ۳۴۲
پرسش
Why does acid strength increase across a row of comparable hydrides?
پاسخ
Increasing electronegativity stabilizes the conjugate base and polarizes the H–A bond.
کارت ۳۴۳
پرسش
What is an amphiprotic species?
پاسخ
A species that can donate or accept a proton, such as HCO₃⁻.
کارت ۳۴۴
پرسش
What amounts remain after a limited amount of strong base partially neutralizes weak acid HA?
پاسخ
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.
کارت ۳۴۵
پرسش
How are Ka, Kb, pKa, and pKb related for a conjugate pair at 25°C?
پاسخ
KaKb = Kw = 1.0 × 10^-14, and pKa + pKb = pKw = 14.00.
کارت ۳۴۶
پرسش
When does pH have little effect on a salt's solubility?
پاسخ
When neither dissolved ion reacts appreciably with H₃O⁺ or OH⁻.
کارت ۳۴۷
پرسش
How does H₂O act in HCl + H₂O → H₃O⁺ + Cl⁻ and in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
پاسخ
It acts as a base in the first reaction by accepting H⁺, and as an acid in the second by donating H⁺.
کارت ۳۴۸
پرسش
After mixing weak base B with strong acid, what controls the final solution in the three stoichiometric regimes?
پاسخ
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⁺.
کارت ۳۴۹
پرسش
What two components make a typical weak-acid buffer?
پاسخ
A weak acid and a significant amount of its conjugate base.
کارت ۳۵۰
پرسش
What do the successive half-equivalence pH values approximate in a diprotic weak-acid titration?
پاسخ
The first approximates pKa₁ and the second approximates pKa₂ because each conjugate pair has equal concentrations at its half-equivalence point.
کارت ۳۵۱
پرسش
Which acid is stronger, one with pKa 2 or pKa 5?
پاسخ
The acid with pKa 2; lower pKa means larger Ka.
کارت ۳۵۲
پرسش
What is the Henderson–Hasselbalch equation?
پاسخ
pH = pKa + log([A⁻]/[HA]).
کارت ۳۵۳
پرسش
Why are larger binary hydrides down a group often stronger acids?
پاسخ
The H–A bond becomes weaker as the central atom grows, so proton release is easier.
کارت ۳۵۴
پرسش
What mainly determines buffer capacity?
پاسخ
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.
کارت ۳۵۵
پرسش
Why does acid increase CaCO₃ solubility?
پاسخ
H₃O⁺ converts CO₃²⁻ to HCO₃⁻ or carbonic acid species, reducing free carbonate and driving more CaCO₃ to dissolve.
کارت ۳۵۶
پرسش
What does pH < pKa imply for a weak-acid pair?
پاسخ
The protonated form HA predominates over A⁻.
کارت ۳۵۷
پرسش
What happens when stoichiometrically equal amounts of a monoprotic weak acid and strong base are mixed?
پاسخ
The weak acid is consumed to its conjugate base; at equivalence, the solution isn't a buffer containing both forms.
کارت ۳۵۸
پرسش
What is [H₃O⁺] when pH = 4.50?
پاسخ
3.2 × 10^-5 M, from [H₃O⁺] = 10^-pH.
کارت ۳۵۹
پرسش
What is the pH of 0.010 M Ba(OH)₂ at 25°C?
پاسخ
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.
کارت ۳۶۰
پرسش
How does a buffer respond to a small amount of added strong acid?
پاسخ
Its conjugate base consumes H⁺, converting to the weak acid and limiting the pH change.
کارت ۳۶۱
پرسش
Why is the equivalence-point solution basic in a monoprotic weak-acid–strong-base titration?
پاسخ
The conjugate base produced at equivalence reacts with water to form OH⁻, so the pH is above neutral—above 7.00 at 25°C.
کارت ۳۶۲
پرسش
How is percent ionization calculated for a weak acid or weak base?
پاسخ
For HA, use ([H₃O⁺]equilibrium ÷ [HA]initial) × 100%. For B, use ([BH⁺]equilibrium ÷ [B]initial) × 100%, under the usual monoprotic setup.
کارت ۳۶۳
پرسش
When is Henderson–Hasselbalch useful for an initial buffer-pH calculation?
پاسخ
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.
کارت ۳۶۴
پرسش
Why does adding oxygen atoms usually strengthen oxyacids with the same central atom?
پاسخ
Extra oxygens withdraw electron density and delocalize negative charge in the conjugate base.
کارت ۳۶۵
پرسش
A prepared buffer is accidentally diluted to twice its intended volume; what happens to its pH and capacity?
پاسخ
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.
کارت ۳۶۶
پرسش
How does adding OH⁻ affect Mg(OH)₂ solubility?
پاسخ
It decreases solubility through the common-ion effect, shifting Mg(OH)₂(s) ⇌ Mg²⁺ + 2OH⁻ toward the solid.
کارت ۳۶۷
پرسش
A buffer has equal [A⁻] and [HA]; what is its pH?
پاسخ
pH = pKa because log(1) = 0.
کارت ۳۶۸
پرسش
How should a weak acid–strong base mixture be solved before equivalence?
پاسخ
First use mole stoichiometry; if both HA and A⁻ remain, use the resulting buffer relation.
کارت ۳۶۹
پرسش
Why can pure neutral water have a pH other than 7.00?
پاسخ
Kw changes with temperature. Neutrality means [H₃O⁺] = [OH⁻], while pH = 7.00 only when Kw = 1.0 × 10^-14 at 25°C.
کارت ۳۷۰
پرسش
25.0 mL of 0.200 M HCl is diluted to 100.0 mL; what is the pH?
پاسخ
1.301. Dilution gives [H₃O⁺] = (0.200 M)(25.0 mL)/(100.0 mL) = 0.0500 M, so pH = -log(0.0500).
کارت ۳۷۱
پرسش
How does a buffer respond to a small amount of added strong base?
پاسخ
The weak acid consumes OH⁻, forming conjugate base and water.
کارت ۳۷۲
پرسش
How do you find the final pH after mixing a strong acid and strong base at 25°C?
پاسخ
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.
کارت ۳۷۳
پرسش
What distinguishes acid strength from acid concentration?
پاسخ
Strength is the equilibrium tendency to donate H⁺, reflected by Ka or pKa; concentration is the amount of acid per solution volume.
کارت ۳۷۴
پرسش
If [A⁻]/[HA] = 10, how does pH compare with pKa?
پاسخ
pH = pKa + 1 because log 10 = 1.
کارت ۳۷۵
پرسش
Which conjugate base is more stable, one with localized or resonance-delocalized charge?
پاسخ
The resonance-delocalized conjugate base, which generally corresponds to the stronger acid.
کارت ۳۷۶
پرسش
Which 1.0 L buffer has greater capacity: 1.0 mol each of HA/A⁻ or 0.10 mol each at the same ratio?
پاسخ
The 1.0 mol pair; both have the same initial pH, but the larger amounts neutralize more added acid or base.
کارت ۳۷۷
پرسش
For BHX(s) ⇌ BH⁺ + X⁻, why can raising pH increase the salt's solubility?
پاسخ
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.
کارت ۳۷۸
پرسش
What does pH > pKa imply for a weak-acid pair?
پاسخ
The deprotonated form A⁻ predominates over HA.
کارت ۳۷۹
پرسش
For HA + B ⇌ A⁻ + BH⁺, which side is favored when pKa(HA) = 4 and pKa(BH⁺) = 9?
پاسخ
Products are favored. Proton transfer moves toward the weaker acid–base pair, and K ≈ 10^(9 − 4) = 10^5.
کارت ۳۸۰
پرسش
What is the pOH when [OH⁻] = 2.5 × 10^-4 M?
پاسخ
3.60, from -log(2.5 × 10^-4).
کارت ۳۸۱
پرسش
What is the pH of 0.100 M HA when Ka = 1.0 × 10^-5?
پاسخ
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.
کارت ۳۸۲
پرسش
Why does a buffer fail after too much strong acid is added?
پاسخ
Its conjugate base is depleted, so added H⁺ is no longer consumed effectively.
کارت ۳۸۳
پرسش
What do two clear equivalence regions on an acid titration curve suggest?
پاسخ
At least two distinguishable titratable protons; on a clean ideal curve with exactly two equivalence regions, this is consistent with a diprotic acid.
کارت ۳۸۴
پرسش
A buffer has pKa 4.8 and [A⁻]/[HA] = 0.10; what is pH?
پاسخ
3.8, from 4.8 + log(0.10).
کارت ۳۸۵
پرسش
Why is HCl stronger than HF in water despite F being more electronegative?
پاسخ
The H–F bond is much stronger; bond strength dominates this down-group binary-acid comparison.
کارت ۳۸۶
پرسش
Why does percent ionization increase when a weak acid is diluted?
پاسخ
Dilution shifts ionization toward more particles, so a larger fraction ionizes even though [H₃O⁺] decreases.
کارت ۳۸۷
پرسش
A buffer contains more HA than A⁻. Which addition can it neutralize in greater amount: strong acid or strong base?
پاسخ
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.
کارت ۳۸۸
پرسش
Why can removing a basic anion increase a salt's molar solubility without changing Ksp?
پاسخ
The equilibrium shifts to replace the consumed ion; Ksp remains fixed at the same temperature.
کارت ۳۸۹
پرسش
Why can an acid–base indicator change color as pH changes?
پاسخ
Its protonated and deprotonated forms have different colors or other observable properties, and their relative amounts change with pH.
کارت ۳۹۰
پرسش
What buffer results from mixing 1.0 mol HA with 0.40 mol OH⁻?
پاسخ
0.60 mol HA and 0.40 mol A⁻ remain, forming a buffer before any equilibrium calculation.
کارت ۳۹۱
پرسش
What is the pH of 0.200 M weak base B when Kb = 2.0 × 10^-5 at 25°C?
پاسخ
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.
کارت ۳۹۲
پرسش
Why does a weak acid alone not make an effective buffer?
پاسخ
It lacks a substantial conjugate-base reserve to consume added strong acid.
کارت ۳۹۳
پرسش
What controls pH after excess strong base passes equivalence?
پاسخ
The concentration of excess OH⁻ after accounting for reaction stoichiometry and total volume.
کارت ۳۹۴
پرسش
How should an indicator be chosen for a titration?
پاسخ
Its color-change range should fall within the steep pH change near the equivalence point.
کارت ۳۹۵
پرسش
How can a measured pH and known pKa give a conjugate-base/acid ratio?
پاسخ
Rearrange Henderson–Hasselbalch: [A⁻]/[HA] = 10^(pH − pKa).
کارت ۳۹۶
پرسش
Can a weak base and its conjugate acid form a buffer?
پاسخ
Yes, when both are present in significant amounts.
کارت ۳۹۷
پرسش
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?
پاسخ
The concentrated buffer changes pH less because it has greater capacity.
کارت ۳۹۸
پرسش
How does equivalence-point pH compare for strong acid–strong base, weak acid–strong base, and weak base–strong acid titrations at 25°C?
پاسخ
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.
کارت ۳۹۹
پرسش
Why should mole ratios replace concentration ratios after mixing buffer solutions?
پاسخ
Both components share the same final volume, so that volume cancels in [A⁻]/[HA].
کارت ۴۰۰
پرسش
How does adding a little strong acid change a buffer's conjugate-base and conjugate-acid amounts?
پاسخ
The conjugate base decreases and its conjugate acid increases by the amount of strong acid consumed.
کارت ۴۰۱
پرسش
What does entropy measure qualitatively?
پاسخ
The dispersal of matter and energy among available microstates.
کارت ۴۰۲
پرسش
How is standard reaction entropy calculated?
پاسخ
ΔS°rxn = ΣνS°(products) − ΣνS°(reactants).
کارت ۴۰۳
پرسش
What equation gives ΔG° from ΔH° and ΔS°, and what standard states do the degree symbols assume?
پاسخ
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.
کارت ۴۰۴
پرسش
Does thermodynamic favorability guarantee a fast reaction?
پاسخ
No. A favorable reaction can be slow when its activation barrier is large.
کارت ۴۰۵
پرسش
What is ΔG at equilibrium?
پاسخ
Zero under the current conditions because there is no net driving force.
کارت ۴۰۶
پرسش
Why can an endothermic dissolution still be thermodynamically favorable?
پاسخ
A sufficiently positive entropy change can make TΔS exceed positive ΔH, giving negative ΔG.
کارت ۴۰۷
پرسش
How can an unfavorable reaction be driven by a favorable one?
پاسخ
Couple them so their equations and ΔG values add to a negative overall ΔG.
کارت ۴۰۸
پرسش
Where does oxidation occur in every electrochemical cell?
پاسخ
At the anode.
کارت ۴۰۹
پرسش
How are standard cell potential and standard free energy related?
پاسخ
ΔG° = -nFE°cell.
کارت ۴۱۰
پرسش
What equation gives cell potential under nonstandard conditions?
پاسخ
E = E° − (RT/nF) ln Q. When Q = 1, ln Q = 0, so E = E°.
کارت ۴۱۱
پرسش
How is electrical charge related to current and time?
پاسخ
q = It.
کارت ۴۱۲
پرسش
Which phase has greater molar entropy, liquid water or ice at the same temperature?
پاسخ
Liquid water because its molecules have more accessible arrangements and motion.
کارت ۴۱۳
پرسش
Do elements in their standard states have zero standard molar entropy?
پاسخ
No. Their ΔHf° is zero, but their absolute S° values are positive above 0 K.
کارت ۴۱۴
پرسش
How do the four ΔH° and ΔS° sign combinations determine thermodynamic favorability across temperature?
پاسخ
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.
کارت ۴۱۵
پرسش
What does it indicate when a thermodynamically favored process does not occur at a measurable rate?
پاسخ
It is under kinetic control, commonly because of a high activation energy; no measurable reaction does not mean the system is at equilibrium.
کارت ۴۱۶
پرسش
How are ΔG° and K related?
پاسخ
ΔG° = -RT ln K.
کارت ۴۱۷
پرسش
What two contributions compete in dissolving an ionic solid?
پاسخ
Enthalpy changes from separating and solvating particles, and entropy changes from their new dispersal and solvent organization.
کارت ۴۱۸
پرسش
What must cancel when coupled reactions are added?
پاسخ
Shared intermediates, leaving the desired net reaction.
کارت ۴۱۹
پرسش
Where does reduction occur in every electrochemical cell?
پاسخ
At the cathode.
کارت ۴۲۰
پرسش
What sign of E°cell indicates a favorable standard galvanic reaction?
پاسخ
Positive E°cell, corresponding to negative ΔG°.
کارت ۴۲۱
پرسش
If Q increases for a galvanic reaction, how does E change at fixed temperature?
پاسخ
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.
کارت ۴۲۲
پرسش
How are moles of electrons found from charge?
پاسخ
Moles e⁻ = q/F, where F ≈ 96485 C mol^-1 e⁻.
کارت ۴۲۳
پرسش
How does producing more gas particles usually affect system entropy?
پاسخ
It increases entropy because the particles have more positional microstates.
کارت ۴۲۴
پرسش
Can a dissolution with negative ΔH be unfavorable?
پاسخ
Yes. A sufficiently negative entropy change at the stated temperature can make ΔG positive.
کارت ۴۲۵
پرسش
When can a process with ΔH > 0 and ΔS > 0 become favorable?
پاسخ
At sufficiently high temperature, when TΔS exceeds ΔH.
کارت ۴۲۶
پرسش
How does a catalyst affect ΔG?
پاسخ
It does not change ΔG; it lowers the activation barrier for both directions.
کارت ۴۲۷
پرسش
For A → B, ΔGf°(A) = -50 kJ mol^-1 and ΔGf°(B) = -80 kJ mol^-1. What is ΔG°rxn?
پاسخ
-30 kJ mol^-1. Use ΣνΔGf°(products) − ΣνΔGf°(reactants) = -80 − (-50).
کارت ۴۲۸
پرسش
Why can dissolving a gas in a liquid have a negative entropy change?
پاسخ
Gas particles lose much of their translational freedom when confined and solvated in the liquid.
کارت ۴۲۹
پرسش
If coupled steps have ΔG values +20 kJ and -35 kJ, what is overall ΔG?
پاسخ
-15 kJ, so the combined process is thermodynamically favorable under those conditions.
کارت ۴۳۰
پرسش
What role does each half-cell solution play in an electrochemical cell?
پاسخ
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.
کارت ۴۳۱
پرسش
How is E°cell found from standard reduction potentials?
پاسخ
E°cell = E°cathode − E°anode, using both tabulated values as reductions.
کارت ۴۳۲
پرسش
How does a cell's potential magnitude change as Q approaches or moves away from K, and what is E at equilibrium?
پاسخ
|E| falls toward zero as Q approaches K and grows as the system moves farther from equilibrium. At equilibrium, Q = K and E = 0.
کارت ۴۳۳
پرسش
How many moles of electrons pass when 1.93 × 10^5 C flows?
پاسخ
2.00 mol e⁻, from q/F.
کارت ۴۳۴
پرسش
How does a salt bridge maintain charge balance in a galvanic cell?
پاسخ
Anions migrate toward the anode compartment and cations toward the cathode compartment, countering the net charge imbalances created by the two half-reactions.
کارت ۴۳۵
پرسش
Why does raising a substance's temperature generally increase its entropy?
پاسخ
Energy spreads across more accessible particle energy states, increasing the number of possible microscopic arrangements.
کارت ۴۳۶
پرسش
When can a process with ΔH < 0 and ΔS < 0 be favorable?
پاسخ
At sufficiently low temperature, where the unfavorable -TΔS term is small.
کارت ۴۳۷
پرسش
Why can diamond persist even though graphite is more stable at standard conditions?
پاسخ
Conversion has a large activation barrier, so diamond is kinetically persistent.
کارت ۴۳۸
پرسش
What do the external circuit and measuring device do in an electrochemical cell?
پاسخ
The circuit carries electrons from anode to cathode; a voltmeter measures potential difference, while an ammeter in series measures current.
کارت ۴۳۹
پرسش
At constant temperature, how does increasing the volume available to a gas affect its entropy?
پاسخ
Entropy increases because the gas particles can occupy more positions in the larger space, so more microstates are accessible.
کارت ۴۴۰
پرسش
How does reversing one coupled reaction affect its ΔG?
پاسخ
It reverses the sign of that reaction's ΔG.
کارت ۴۴۱
پرسش
Why is n required in ΔG° = -nFE°?
پاسخ
It is the moles of electrons transferred per balanced reaction, linking charge flow to reaction extent.
کارت ۴۴۲
پرسش
What makes an electrolytic cell operate?
پاسخ
An external power source drives a thermodynamically unfavorable redox reaction; oxidation still occurs at the anode and reduction at the cathode.
کارت ۴۴۳
پرسش
In an Mⁿ⁺/M concentration cell, which half-cell is the anode: the dilute or concentrated ion solution?
پاسخ
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.
کارت ۴۴۴
پرسش
How is deposited metal mass found from current and time?
پاسخ
Find q = It, convert q/F to moles e⁻, use the half-reaction ratio to moles metal, then multiply by molar mass.
کارت ۴۴۵
پرسش
Given product S° total 500 J mol^-1 K^-1 and reactant total 420 J mol^-1 K^-1, what is ΔS°?
پاسخ
+80 J mol^-1 K^-1.
کارت ۴۴۶
پرسش
How do electrode masses change in a Zn–Cu galvanic cell?
پاسخ
The Zn anode loses mass as Zn → Zn²⁺ + 2e⁻, while the Cu cathode gains mass as Cu²⁺ + 2e⁻ → Cu.
کارت ۴۴۷
پرسش
What is ΔG° when ΔH° = 50 kJ mol^-1, ΔS° = 0.200 kJ mol^-1 K^-1, and T = 300 K?
پاسخ
-10 kJ mol^-1, from ΔG° = 50 − (300)(0.200).
کارت ۴۴۸
پرسش
Why can temperature change a solid's solubility?
پاسخ
Temperature changes the balance of ΔH and TΔS, so it changes the free energy of dissolution and the equilibrium constant.
کارت ۴۴۹
پرسش
What does the size of ΔG° relative to RT imply about K?
پاسخ
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.
کارت ۴۵۰
پرسش
Bubbles form at an inert cathode in acidic solution; which half-reaction can explain them?
پاسخ
2H⁺ + 2e⁻ → H₂(g). Gas evolution at the cathode can be direct evidence of reduction.
۴۵۰ کارت
AP Chemistry Flashcards: Complete 9-Unit Course Review
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