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