Your FREE AP Chemistry Practice Test 2026 – 240+ Q&A

Correct answer: 2 moles

2 moles is the correct answer. Dividing the 88-gram sample by the molar mass of 44 grams per mole yields 2 moles, applying the standard relationship that amount in moles equals mass divided by molar mass.

Correct answer: It exists as essentially one isotope

It exists as essentially one isotope is the correct answer. A single peak in a mass spectrum means nearly all atoms share the same mass, so the element is effectively monoisotopic with no significant lighter or heavier forms.

Correct answer: The heavier isotope of mass 11 is more abundant

The heavier isotope of mass 11 being more abundant is the correct answer. Because the weighted average is pulled toward 11, the isotope of mass 11 must make up the larger fraction of naturally occurring boron atoms.

Correct answer: The molar mass and Avogadro's number

The molar mass and Avogadro's number is the correct answer. Mass is divided by molar mass to get moles, and moles are multiplied by Avogadro's number to find the count of molecules in the sample.

Correct answer: Five peaks

Five peaks is the correct answer. Phosphorus has electrons in the 1s, 2s, 2p, 3s, and 3p subshells, and each of these five occupied subshells produces a separate peak at its own binding energy.

Correct answer: A filled 2s subshell and a filled 2p subshell

A filled 2s and filled 2p subshell is the correct answer. A full s subshell holds two electrons and a full p subshell holds six, giving a 2 to 6, or 1 to 3, ratio of peak heights in the spectrum.

Correct answer: The net positive charge felt by an electron after accounting for shielding

The net positive charge felt by an electron after accounting for shielding is the correct answer. Effective nuclear charge equals the actual nuclear charge reduced by the screening effect of inner electrons that lie between the nucleus and the electron in question.

Correct answer: Core electrons lie between the nucleus and the valence electrons

Core electrons lying between the nucleus and the valence electrons is the correct answer. Their position closer to the nucleus lets them block, or screen, much of the nuclear attraction, while valence electrons at similar distances shield one another only weakly.

Correct answer: The s subshell because it penetrates closer to the nucleus

The s subshell because it penetrates closer to the nucleus is the correct answer. Greater penetration lets s electrons experience a higher effective nuclear charge and less shielding, lowering their energy relative to p and d subshells in the same shell.

Correct answer: 1s2 2s2 2p6 3s2

1s2 2s2 2p6 3s2 is the correct answer. Filling subshells in order of increasing energy places two electrons in 1s, two in 2s, six in 2p, and the final two in 3s, accounting for all twelve of magnesium's electrons.

Correct answer: It becomes identical to that of a noble gas with a filled 3p subshell

Becoming identical to a noble gas with a filled 3p subshell is the correct answer. Sulfur has the configuration ending in 3p4, and gaining two electrons fills the 3p subshell to 3p6, matching the stable configuration of argon.

Correct answer: Carbon

Carbon is the correct answer. Moving left to right across the second period increases effective nuclear charge and decreases atomic radius, so carbon, farthest right of the four, holds its outer electron most tightly and has the highest first ionization energy.

Correct answer: Fewer electrons, reducing electron-electron repulsion

Fewer electrons, reducing electron-electron repulsion is the correct answer. Removing electrons to form a cation leaves the remaining electrons more strongly attracted by the unchanged nuclear charge, so the cation is smaller than its parent atom.

Correct answer: The attraction increases

The attraction increases is the correct answer. Coulombic force is directly proportional to the product of the interacting charges, so a larger positive nuclear charge pulls a given electron more strongly toward the nucleus.

Correct answer: The ground-state electron is in the lowest, most tightly bound energy level

The ground-state electron being in the lowest, most tightly bound level is the correct answer. An electron in the ground state sits closest to the nucleus at the lowest energy, so removing it requires more energy than removing an electron already raised to a higher, less tightly held level.

Correct answer: $\ce{H2O}$

$\ce{H2O}$ is the correct answer. An empirical formula expresses the simplest whole-number ratio of atoms, and a 2-to-1 ratio of hydrogen to oxygen corresponds directly to the formula $\ce{H2O}$.

Correct answer: Fluorine has one more proton, increasing the pull on the same shell

Fluorine having one more proton is the correct answer. The extra proton raises the effective nuclear charge acting on electrons in the same principal shell, drawing them inward and making fluorine's radius smaller than that of oxygen.

Correct answer: The 2p electrons are held less tightly than the 2s electrons

The 2p electrons being held less tightly is the correct answer. Within the same shell, 2s electrons penetrate closer to the nucleus and feel a higher effective nuclear charge, so they have a higher binding energy than the less penetrating 2p electrons.

Correct answer: Sodium ion, neon, fluoride ion

Sodium ion, neon, fluoride ion is the correct answer. All three have ten electrons, so the species with the most protons, the sodium ion, pulls them in most tightly and is smallest, while the fluoride ion with the fewest protons is largest.

Correct answer: Atoms gain electrons more readily as effective nuclear charge increases

Atoms gaining electrons more readily as effective nuclear charge increases is the correct answer. A higher effective nuclear charge across a period more strongly attracts an added electron, releasing more energy and making the electron affinity more negative.

Correct answer: The electron jumps to a higher allowed energy level

The electron jumps to a higher allowed energy level is the correct answer. Absorbing a photon whose energy matches the gap between levels excites the electron from a lower to a higher quantized orbit, consistent with discrete atomic energy levels.

Correct answer: 30 grams per mole

30 grams per mole is the correct answer. The sample contains one tenth of a mole because $6.02 \times 10^{22}$ is one tenth of Avogadro's number, so dividing 3.0 grams by 0.1 mole gives a molar mass of 30 grams per mole.

Correct answer: Magnesium oxide ions carry larger charges than sodium chloride ions

Larger ionic charges in magnesium oxide is the correct answer. Coulomb's law shows lattice energy increases with the product of the ionic charges, and the doubly charged $\ce{Mg^2+}$ and $\ce{O^2-}$ ions attract far more strongly than the singly charged $\ce{Na+}$ and $\ce{Cl-}$ ions, giving a higher melting point.

Correct answer: Polar covalent or ionic

Polar covalent or ionic is the correct answer. As the electronegativity difference grows, electron sharing becomes increasingly unequal, shifting the bond from polar covalent toward ionic, where electrons are essentially transferred.

Correct answer: Seesaw

Seesaw is the correct answer. Five electron domains give a trigonal bipyramidal electron arrangement, and placing the single lone pair in an equatorial position leaves the four bonded atoms in a seesaw shape.

Correct answer: Square planar

Square planar is the correct answer. Six electron domains form an octahedral arrangement, and placing the two lone pairs on opposite sides leaves the four bonded fluorine atoms in one plane, a square planar shape.

Correct answer: Sp hybridized

sp hybridized is the correct answer. Each carbon forms two sigma bonds with a linear arrangement, requiring two sp hybrid orbitals, while the two remaining unhybridized p orbitals form the two pi bonds of the triple bond.

Correct answer: One sigma bond and two pi bonds

One sigma bond and two pi bonds is the correct answer. A triple bond always contains a single sigma bond from head-on orbital overlap plus two pi bonds formed by the side-to-side overlap of two pairs of unhybridized p orbitals.

Correct answer: Electron delocalization spreads the bonding evenly, making all bonds equivalent

Electron delocalization making all bonds equivalent is the correct answer. The pi electrons are spread across all three nitrogen-oxygen bonds rather than fixed in one location, so each bond is identical, intermediate between a single and double bond.

Correct answer: An electron-deficient molecule with an incomplete octet

An electron-deficient molecule with an incomplete octet is the correct answer. Boron forms three bonds and remains surrounded by only six valence electrons, falling short of an octet, which makes boron trifluoride a stable exception that acts as an electron-pair acceptor.

Correct answer: An expanded octet with more than eight electrons

An expanded octet is the correct answer. Phosphorus, a period 3 element, can accommodate ten electrons in its valence shell by using available d-orbital space, allowing it to form five bonds in phosphorus pentachloride.

Correct answer: 109.5 degrees

109.5 degrees is the correct answer. Four bonding domains around a central atom adopt a tetrahedral arrangement that maximizes separation, producing the characteristic tetrahedral bond angle of approximately 109.5 degrees.

Correct answer: Slightly smaller than 109.5 degrees

Slightly smaller than 109.5 degrees is the correct answer. The lone pair on nitrogen repels the bonding pairs more strongly than they repel each other, compressing the H-N-H angle to about 107 degrees, just below the ideal tetrahedral value.

Correct answer: An ionic bond that conducts when molten or dissolved but not as a solid

An ionic bond that conducts when molten or dissolved is the correct answer. Metal-nonmetal combinations transfer electrons to form ions, and these ions are locked in place in the solid but become mobile and conductive once the compound is melted or dissolved in water.

Correct answer: Single, double, triple

Single, double, triple is the correct answer. As bond order increases, more shared electron pairs hold the nuclei together more strongly, so bond energy rises from the single bond to the double bond to the strongest triple bond.

Correct answer: Chloroform's bond dipoles do not cancel because of its less symmetric arrangement

Chloroform's bond dipoles not canceling is the correct answer. In carbon tetrachloride the four identical bond dipoles point symmetrically and cancel, but replacing one chlorine with hydrogen in chloroform breaks that symmetry so the dipoles no longer cancel, leaving a net dipole.

Correct answer: A semiconductor has a small band gap that electrons can cross with modest energy

A small band gap electrons can cross is the correct answer. In a semiconductor the energy gap between the filled valence band and empty conduction band is small enough that added energy promotes electrons into the conduction band, unlike an insulator's large gap.

Correct answer: They are structural isomers

They are structural isomers is the correct answer. Compounds with the same molecular formula but different arrangements of their atoms are structural isomers, which is why the same formula $\ce{C2H6O}$ can describe both an alcohol and an ether with distinct properties.

Correct answer: Hydrogen bonding

Hydrogen bonding is the correct answer. Water's O-H bonds let each molecule form strong hydrogen bonds with neighbors, which requires extra energy to break and raises the boiling point well above that of similarly sized molecules lacking such bonds.

Correct answer: Fluorine, oxygen, or nitrogen

Fluorine, oxygen, or nitrogen is the correct answer. Hydrogen bonding requires hydrogen attached to one of these small, highly electronegative atoms, which creates the strong partial charges needed for the interaction.

Correct answer: Dipole-dipole forces

Dipole-dipole forces is the correct answer. Polar molecules have permanent dipoles, so the positive end of one molecule attracts the negative end of another, producing dipole-dipole attractions between them.

Correct answer: Temporary, instantaneous dipoles from shifting electron clouds

Temporary instantaneous dipoles is the correct answer. London dispersion forces come from the constant random movement of electrons, which momentarily creates uneven charge distributions that induce dipoles in neighboring molecules.

Correct answer: A larger, more polarizable electron cloud

A larger, more polarizable electron cloud is the correct answer. More electrons spread over a larger volume are easier to distort, producing stronger temporary dipoles and therefore stronger London dispersion forces.

Correct answer: A sodium ion surrounded by water molecules in solution

A sodium ion surrounded by water molecules is the correct answer. Ion-dipole forces occur when an ion attracts the oppositely charged end of a polar molecule, as happens when water hydrates dissolved ions.

Correct answer: Branched molecules have a smaller surface area for contact, weakening dispersion forces

Smaller surface area for contact is the correct answer. A more compact, branched shape reduces the surface contact between molecules, weakening London dispersion forces and lowering the boiling point compared with an extended straight chain.

Correct answer: Vapor pressure decreases

Vapor pressure decreases is the correct answer. Stronger intermolecular forces hold molecules in the liquid more tightly, so fewer escape into the vapor phase, lowering the measured vapor pressure.

Correct answer: Volatile

Volatile is the correct answer. A volatile liquid evaporates readily because its weak intermolecular forces allow many molecules to enter the vapor phase, giving it a high vapor pressure.

Correct answer: The external atmospheric pressure

The external atmospheric pressure is the correct answer. Boiling occurs throughout a liquid when its vapor pressure rises to match the surrounding pressure, allowing bubbles of vapor to form within the liquid.

Correct answer: The atmospheric pressure is lower, so vapor pressure matches it sooner

Lower atmospheric pressure is the correct answer. At high altitude the reduced air pressure means the liquid's vapor pressure equals the surroundings at a lower temperature, so boiling occurs below 100 degrees Celsius.

Correct answer: Viscosity

Viscosity is the correct answer. Viscosity reflects internal resistance to flow, and liquids with stronger intermolecular attractions, such as honey, have higher viscosity than those with weak forces.

Correct answer: Covalent network solid

Covalent network solid is the correct answer. In a covalent network solid such as diamond, every atom is bonded to its neighbors by strong covalent bonds throughout the crystal, requiring enormous energy to melt.

Correct answer: They contain delocalized electrons that move freely

Delocalized electrons that move freely is the correct answer. Metallic bonding produces a sea of delocalized valence electrons that can drift through the lattice, allowing metals to conduct electricity even as solids.

Correct answer: Relatively weak intermolecular forces between discrete molecules

Relatively weak intermolecular forces is the correct answer. Molecular solids consist of individual molecules held together only by intermolecular attractions, which are far weaker than the bonds in ionic or covalent network solids, so they melt easily.

Correct answer: In the solid, ions are locked in place, but melting frees them to move

Ions locked in place until melting is the correct answer. Conduction requires mobile charge carriers; in solid sodium chloride the ions are fixed in the lattice, but melting allows the ions to move and carry current.

Correct answer: One half

One half is the correct answer. Boyle's law makes pressure and volume inversely proportional at constant temperature, so doubling the pressure reduces the volume to half its original value.

Correct answer: The number of moles of gas

The number of moles of gas is the correct answer. In the ideal gas law relating pressure, volume, temperature, and amount, the symbol n stands for the quantity of gas measured in moles.

Correct answer: Kelvin

Kelvin is the correct answer. Gas law calculations require absolute temperature in kelvin because the relationships are based on a scale that starts at absolute zero, where particle motion is at a minimum.

Correct answer: The pressure decreases

The pressure decreases is the correct answer. At constant volume, pressure is directly proportional to absolute temperature, so cooling the gas reduces the kinetic energy of its particles and lowers the pressure.

Correct answer: Perfectly elastic, conserving total kinetic energy

Perfectly elastic is the correct answer. Kinetic molecular theory assumes gas particle collisions are perfectly elastic, meaning no kinetic energy is lost when particles collide with each other or the container walls.

Correct answer: Collisions of gas particles with the container walls

Collisions with the container walls is the correct answer. Gas pressure results from the countless impacts of fast-moving particles striking the container surfaces, with more frequent or forceful collisions producing higher pressure.

Correct answer: The same average kinetic energy

The same average kinetic energy is the correct answer. Average kinetic energy depends only on temperature, so two gases at the same temperature share the same average kinetic energy even though their speeds differ with molar mass.

Correct answer: Water vapor

Water vapor is the correct answer. A gas collected over water becomes saturated with water vapor, so by Dalton's law the total pressure is the sum of the dry gas pressure and the water vapor pressure.

Correct answer: Low temperature where attractions become significant

Low temperature where attractions become significant is the correct answer. At low temperature the slower particles are more affected by intermolecular attractions, causing the gas to deviate noticeably from ideal behavior.

Correct answer: Helium, a small nonpolar atom with weak forces

Helium is the correct answer. Helium atoms are tiny and experience only very weak intermolecular forces, so they closely approximate the ideal gas assumptions of negligible volume and no attractions.

Correct answer: Higher molar mass gives higher gas density

Higher molar mass gives higher density is the correct answer. At the same temperature and pressure equal volumes hold equal numbers of molecules, so a gas with heavier molecules packs more mass into that volume and is denser.

Correct answer: The total mass of the solution

The total mass of the solution is the correct answer. Mass percent expresses concentration as the mass of solute divided by the total mass of the solution, then multiplied by 100 to give a percentage.

Correct answer: Extremely dilute

Extremely dilute is the correct answer. Parts per million expresses very small amounts of solute relative to the solution, making it convenient for trace concentrations such as pollutants in water.

Correct answer: Conduct electricity as an electrolyte

Conduct electricity as an electrolyte is the correct answer. The mobile ions produced when an ionic compound dissociates allow the solution to carry electric current, classifying it as an electrolyte.

Correct answer: Remains as neutral molecules without producing ions

Remains as neutral molecules is the correct answer. Sugar is a molecular compound that dissolves without dissociating into ions, so its solution lacks the mobile charges needed to conduct electricity and is a nonelectrolyte.

Correct answer: Separate solute particles and pull solvent molecules apart

Separate solute and solvent particles is the correct answer. Dissolving requires energy to overcome the attractions among solute particles and among solvent particles before new solute-solvent interactions can form.

Correct answer: More dissolved solute than normally possible

More dissolved solute than normally possible is the correct answer. A supersaturated solution holds more dissolved solute than its saturation point allows, an unstable condition usually formed by carefully cooling a hot saturated solution.

Correct answer: The excess solute rapidly crystallizes out

The excess solute rapidly crystallizes out is the correct answer. A seed crystal gives the unstable excess solute a surface to deposit on, triggering rapid crystallization until the solution returns to saturation.

Correct answer: Evaporation of the water to leave the solid salt

Evaporation of the water is the correct answer. Because the salt is dissolved and passes through filters, removing the water by evaporation leaves the solid salt behind, accomplishing the separation.

Correct answer: The distance traveled by the solvent front

The distance traveled by the solvent front is the correct answer. The retention factor compares how far a component moved to how far the solvent front advanced, giving a value between zero and one that characterizes the component.

Correct answer: It traveled a large fraction of the solvent distance

It traveled a large fraction of the solvent distance is the correct answer. A high retention factor means the component moved nearly as far as the solvent front, indicating it interacts more with the mobile phase than the stationary phase.

Correct answer: The threshold frequency

The threshold frequency is the correct answer. The photoelectric effect requires each photon to carry enough energy to free an electron, so light below the metal's threshold frequency ejects no electrons regardless of its intensity.

Correct answer: The number of electrons ejected per second

The number of electrons ejected per second is the correct answer. Above the threshold, brighter light delivers more photons, ejecting more electrons, although the kinetic energy of each electron depends on frequency, not intensity.

Correct answer: Known concentrations of standard solutions

Known concentrations of standard solutions is the correct answer. Plotting measured absorbance versus known concentrations produces a straight calibration line that lets an unknown sample's concentration be read from its absorbance.

Correct answer: Dipole-dipole forces

Dipole-dipole forces is the correct answer. When molecules possess permanent dipoles, the positive end of one molecule attracts the negative end of a neighboring molecule, creating dipole-dipole attractions.

Correct answer: Fluorine, oxygen, or nitrogen

Fluorine, oxygen, or nitrogen is the correct answer. Hydrogen bonding is an especially strong dipole interaction that requires hydrogen to be attached to one of these small, highly electronegative atoms.

Correct answer: Ion-dipole force

Ion-dipole force is the correct answer. An ion-dipole interaction forms between a charged ion and the partial charges of a polar molecule such as water, and it is central to dissolving ionic compounds.

Correct answer: Higher polarizability allows larger temporary dipoles to form

Higher polarizability is the correct answer. A larger, more polarizable electron cloud can shift more readily, producing larger instantaneous dipoles and therefore stronger London dispersion attractions.

Correct answer: Covalent network solid

Covalent network solid is the correct answer. In a covalent network solid like diamond, every atom is joined to its neighbors by strong covalent bonds extending throughout the structure, requiring great energy to break apart.

Correct answer: Relatively weak intermolecular forces

Relatively weak intermolecular forces is the correct answer. Molecular solids consist of discrete molecules held in place only by intermolecular attractions, which are far weaker than covalent or ionic bonds, so they melt at low temperatures.

Correct answer: Lower vapor pressure at a given temperature

Lower vapor pressure is the correct answer. Strong intermolecular forces hold molecules in the liquid more tightly, so fewer molecules escape into the vapor and the equilibrium vapor pressure is lower.

Correct answer: Viscosity

Viscosity is the correct answer. Viscosity measures a liquid's resistance to flow, and stronger intermolecular attractions among honey's molecules give it a high viscosity compared with water.

Correct answer: Molality

Molality is the correct answer. Molality is defined as moles of solute divided by kilograms of solvent, a unit that does not change with temperature because it relies on mass rather than volume.

Correct answer: Milligrams of solute per kilogram of solution

Milligrams of solute per kilogram of solution is the correct answer. One part per million corresponds to one milligram of solute in one kilogram of solution, a convenient way to express extremely small concentrations.

Correct answer: The total mass of the solution

The total mass of the solution is the correct answer. Mass percent equals the solute mass divided by the total solution mass, times 100, expressing composition as a percentage by mass.

Correct answer: It decreases as molar mass increases

It decreases as molar mass increases is the correct answer. Root-mean-square speed is inversely related to $\sqrt{\text{molar mass}}$, so at the same temperature heavier molecules move more slowly than lighter ones.

Correct answer: The vapor pressure of water

The vapor pressure of water is the correct answer. A gas collected over water is mixed with water vapor, so by Dalton's law the water vapor pressure is subtracted from the total to obtain the partial pressure of the dry gas.

Correct answer: Without long-range order, lacking a regular repeating pattern

Without long-range order is the correct answer. An amorphous solid such as glass has particles fixed in place but lacking the regular, repeating arrangement found in crystalline solids.

Correct answer: No net reaction took place and all ions are spectators

No net reaction took place is the correct answer. When mixing two solutions yields no precipitate, gas, or water, all ions remain dissolved and unchanged as spectators, so there is no net ionic reaction.

Correct answer: Soluble strong electrolytes in aqueous solution

Soluble strong electrolytes in aqueous solution is the correct answer. In a complete ionic equation, soluble strong electrolytes are written as dissociated ions, while solids, liquids, and gases are kept in their molecular form.

Correct answer: Plus 6

Plus 6 is the correct answer. With four oxygens contributing minus 8 total and the overall ion charge being minus 2, sulfur must be plus 6 so the oxidation numbers sum to the ion charge.

Correct answer: It is oxidized as it loses electrons

It is oxidized as it loses electrons is the correct answer. Magnesium goes from an oxidation state of zero to plus 2 by losing electrons, which is the definition of being oxidized.

Correct answer: Double-replacement precipitation

Double-replacement precipitation is the correct answer. The cations and anions exchange partners to form lead iodide, an insoluble yellow solid that precipitates, which is a double-replacement precipitation reaction.

Correct answer: 4 moles

4 moles is the correct answer. The mole ratio of hydrogen to ammonia is 3 to 2, so 6 moles of hydrogen produces 4 moles of ammonia.

Correct answer: 4

4 is the correct answer. The balanced equation is $\ce{4Fe + 3O2 -> 2Fe2O3}$, which provides equal numbers of iron and oxygen atoms on both sides.

Correct answer: To calculate the moles of base used to reach the equivalence point

To calculate the moles of base used is the correct answer. The measured volume of titrant, combined with its known concentration, gives the moles of base needed to reach the equivalence point and thus the moles of acid.

Correct answer: 0.00600 mole

0.00600 mole is the correct answer. Multiplying the volume of 0.0300 liter by the concentration of 0.200 molar gives 0.00600 mole of hydroxide ion.

Correct answer: One compound breaks down into two or more simpler substances

One compound breaks down into simpler substances is the correct answer. A decomposition reaction takes a single compound and splits it into two or more simpler products, which is the opposite of synthesis.

Correct answer: Carbon monoxide

Carbon monoxide is the correct answer. When oxygen is limited, incomplete combustion can produce carbon monoxide or soot rather than fully oxidizing all carbon to carbon dioxide.

Correct answer: The reactant needed in the 2 ratio, since only enough is present for 2 of the first

The reactant needed in the 2 ratio is the correct answer. With only 4 moles of the reactant required at twice the rate, just 2 moles of the first reactant can react, so the 2-ratio reactant runs out first and limits the reaction.

Correct answer: 80.0 percent

80.0 percent is the correct answer. Dividing the actual yield of 40.0 grams by the theoretical yield of 50.0 grams and multiplying by 100 gives a percent yield of 80.0 percent.

Correct answer: It allows the precise concentration of a titrant to be established

It allows the precise concentration of a titrant to be established is the correct answer. A primary standard's known purity and mass let a chemist standardize a solution, giving an accurate titrant concentration for later analyses.

Correct answer: Reduction

Reduction is the correct answer. Gaining electrons lowers the copper ion's oxidation state from plus 2 to zero, and a gain of electrons is by definition a reduction half-reaction.

Correct answer: It gains electrons and is itself reduced

It gains electrons and is itself reduced is the correct answer. The oxidizing agent causes another species to be oxidized by accepting its electrons, and in doing so the oxidizing agent is reduced.

Correct answer: Aluminum must be more reactive than copper in the activity series

Aluminum must be more reactive than copper is the correct answer. A single-replacement reaction proceeds only when the free metal is higher in the activity series than the metal ion it displaces, and aluminum outranks copper.

Correct answer: By using stoichiometry from the limiting reactant and the balanced equation

By using stoichiometry from the limiting reactant is the correct answer. The theoretical yield is calculated from the moles of limiting reactant and the mole ratios in the balanced equation, predicting the maximum possible product.

Correct answer: 6 moles

6 moles is the correct answer. The mole ratio of potassium chlorate to oxygen is 2 to 3, so 4 moles of potassium chlorate yields 6 moles of oxygen gas.

Correct answer: Bubbles form and rise out of the mixture

Bubbles form and rise out of the mixture is the correct answer. The steady release of bubbles that escape the solution is direct evidence that a gaseous product has been generated by the reaction.

Correct answer: Sodium and chloride ions

Sodium and chloride ions is the correct answer. Barium and sulfate combine into the insoluble precipitate, while the sodium and chloride ions remain dissolved and unchanged, making them the spectators.

Correct answer: Because charge must be conserved just as atoms are conserved

Because charge must be conserved is the correct answer. A correct net ionic equation balances both the number of atoms and the total electrical charge on each side, since charge, like mass, is conserved in a reaction.

Correct answer: The elapsed time interval

The elapsed time interval is the correct answer. Average rate equals the change in a reactant or product concentration divided by the change in time over the interval being measured.

Correct answer: A disappears twice as fast as B appears

A disappears twice as fast is the correct answer. Stoichiometry shows two A consumed for each B formed, so the magnitude of A's rate of disappearance is twice the rate B appears.

Correct answer: The rate constant

The rate constant is the correct answer. The proportionality factor k in a rate law is called the rate constant, and its value depends on temperature and the presence of a catalyst.

Correct answer: The natural log of the reactant concentration

The natural log of the reactant concentration is the correct answer. A first-order reaction gives a linear plot when ln of the concentration is graphed versus time, with a slope of negative k.

Correct answer: Second order

Second order is the correct answer. A second-order reaction in a single reactant gives a straight line when the inverse of the concentration is plotted against time, with a slope equal to k.

Correct answer: Zero order

Zero order is the correct answer. For a zero-order reaction the concentration decreases linearly with time, so a plot of concentration versus time is a straight line whose slope equals negative k.

Correct answer: Zero order

Zero order is the correct answer. If changing a reactant's concentration has no effect on the rate, the reaction is zero order with respect to that reactant.

Correct answer: Second order

Second order is the correct answer. When doubling a concentration multiplies the rate by four, which is two squared, the reaction is second order with respect to that reactant.

Correct answer: Inverse seconds

Inverse seconds is the correct answer. Because a first-order rate equals k times a concentration, k must carry units of reciprocal time so the product yields molarity per second.

Correct answer: Temperature and activation energy

Temperature and activation energy is the correct answer. The Arrhenius equation relates the rate constant to the absolute temperature and the activation energy through an exponential term.

Correct answer: The frequency factor

The frequency factor is the correct answer. The A term, also called the pre-exponential or frequency factor, reflects the frequency of collisions with correct orientation in the Arrhenius model.

Correct answer: Second order

Second order is the correct answer. The overall order is the sum of the individual orders, so first order in A plus first order in B gives an overall order of two.

Correct answer: The slow first step

The slow first step is the correct answer. When the first step is rate-determining, the overall rate law is written from that slow step, using only species present in or before it.

Correct answer: A homogeneous catalyst is in the same phase as the reactants

In the same phase as the reactants is the correct answer. A homogeneous catalyst exists in the same physical phase as the reactants, while a heterogeneous catalyst is in a different phase, such as a solid in a gas reaction.

Correct answer: It is consumed in an early step and regenerated in a later step

Consumed early and regenerated later is the correct answer. A catalyst is used up in one step of the mechanism and reformed in a subsequent step, so it does not appear in the overall balanced equation.

Correct answer: The curve shifts so more molecules have high energies

More molecules have high energies is the correct answer. Raising temperature broadens and flattens the Maxwell-Boltzmann curve, shifting it so a larger fraction of molecules exceed the activation energy.

Correct answer: One half

One half is the correct answer. By definition, one half-life is the time required for the reactant concentration to drop to one-half of its initial value.

Correct answer: Unimolecular

Unimolecular is the correct answer. An elementary step in which one molecule reacts on its own, such as a decomposition, is called unimolecular.

Correct answer: Bimolecular

Bimolecular is the correct answer. An elementary step involving the collision of two reactant species is called bimolecular, the most common type of elementary step.

Correct answer: The forward activation energy is smaller than the reverse

The forward activation energy is smaller is the correct answer. In an exothermic reaction the products lie below the reactants, so the barrier from reactants to the peak is smaller than the barrier from products back to the peak.

Correct answer: Three molecules colliding simultaneously with proper orientation is highly improbable

A simultaneous three-body collision is highly improbable is the correct answer. Termolecular steps require three particles to collide at the same instant with correct orientation, an event so unlikely that such steps are uncommon.

Correct answer: Express the intermediate in terms of reactants using the prior fast equilibrium

Express the intermediate in terms of reactants is the correct answer. Because intermediates cannot appear in the final rate law, a preceding fast equilibrium is used to substitute the intermediate with measurable reactant concentrations.

Correct answer: The system

The system is the correct answer. In thermochemistry the system is the specific portion of the universe under study, while everything else, such as the container and air, is collectively called the surroundings.

Correct answer: Heat is energy transferred due to a temperature difference, while temperature measures average kinetic energy of particles

Heat is transferred energy and temperature is average kinetic energy is the correct answer. Heat is the flow of thermal energy between objects at different temperatures, whereas temperature is a measure of the average kinetic energy of the particles in a sample.

Correct answer: Positive

Positive is the correct answer. By convention, heat flowing into the system is given a positive q because the system gains thermal energy, which is the case for an endothermic process.

Correct answer: From the warmer block to the cooler block

From the warmer block to the cooler block is the correct answer. Thermal energy spontaneously transfers from the higher-temperature object to the lower-temperature object until both reach the same temperature.

Correct answer: An entire given object or sample by one degree

An entire object or sample by one degree is the correct answer. Heat capacity is the energy required to raise the temperature of a whole given sample by one degree, while specific heat capacity is stated per gram of substance.

Correct answer: A larger temperature increase

A larger temperature increase is the correct answer. A lower specific heat means less energy is needed per degree of warming, so for the same heat input that metal rises more in temperature than one with a higher specific heat.

Correct answer: Joules

Joules is the correct answer. The quantity of heat q is an energy term, so it is expressed in joules (or kilojoules), with mass in grams, specific heat in joules per gram per degree, and temperature change in degrees.

Correct answer: A solute dissolves in a solvent to form a solution

A solute dissolves in a solvent is the correct answer. The enthalpy of solution is the overall heat absorbed or released when a solute is fully dissolved in a solvent to make a solution.

Correct answer: Endothermic, absorbing heat

Endothermic is the correct answer. The cold pack absorbs heat from its surroundings as the salt dissolves, lowering the temperature, which is the defining feature of an endothermic dissolving process.

Correct answer: It releases 286 kilojoules per mole of reaction

It releases 286 kilojoules per mole is the correct answer. A negative molar enthalpy means the reaction gives off that quantity of energy to the surroundings per mole, identifying it as exothermic.

Correct answer: Increased kinetic motion of surrounding particles

Increased kinetic motion of surrounding particles is the correct answer. Energy released by the reaction transfers to surrounding particles, raising their average kinetic energy and therefore the temperature of the surroundings.

Correct answer: Separate molecules by overcoming intermolecular attractions

Separate molecules by overcoming intermolecular attractions is the correct answer. During a phase change the added energy works against intermolecular forces to convert liquid to vapor rather than increasing kinetic energy, so temperature holds steady.

Correct answer: Phase changes occurring at constant temperature

Phase changes at constant temperature is the correct answer. The horizontal segments of a heating curve represent melting or boiling, where added heat drives the phase change while the temperature remains unchanged.

Correct answer: The metal loses an equal magnitude of heat to what the water gains

Equal magnitude of heat is the correct answer. With no heat lost to the environment, energy conservation requires that the heat released by the cooling metal equals in magnitude the heat absorbed by the warming water.

Correct answer: It insulates the contents to minimize heat exchange with the surroundings

It insulates to minimize heat exchange is the correct answer. The styrofoam acts as an insulator, limiting heat flow between the reaction mixture and the outside so the measured temperature change reflects the reaction itself.

Correct answer: Divide the heat by the moles of the limiting reactant and convert to kilojoules

Divide by moles and convert to kilojoules is the correct answer. Dividing the total heat by the moles of reactant gives energy per mole, and converting joules to kilojoules yields the molar enthalpy in kilojoules per mole.

Correct answer: The sum of the formation enthalpies of the reactants

The sum of the formation enthalpies of the reactants is the correct answer. The reaction enthalpy equals the total standard formation enthalpies of the products minus those of the reactants, each weighted by its coefficient.

Correct answer: Its coefficient from the balanced equation

Its coefficient from the balanced equation is the correct answer. Because enthalpy is extensive, each substance's standard formation enthalpy is scaled by its stoichiometric coefficient before the products and reactants are summed.

Correct answer: Bond enthalpies are average values that vary slightly between different molecules

They are average values that vary between molecules is the correct answer. Tabulated bond enthalpies are averages taken over many compounds, so a calculation using them yields an estimate rather than the exact reaction enthalpy.

Correct answer: Endothermic

Endothermic is the correct answer. When more energy goes into breaking reactant bonds than is recovered from forming product bonds, the net enthalpy change is positive and the reaction absorbs energy overall.

Correct answer: Hess's law

Hess's law is the correct answer. Because enthalpy is a state function, Hess's law lets a hard-to-measure reaction enthalpy be obtained by adding the enthalpies of a chosen set of reactions that combine to give the target reaction.

Correct answer: 10 degrees Celsius

10 degrees Celsius is the correct answer. Rearranging q equals m times c times the temperature change gives 4180 joules divided by the product of 100 grams and 4.18 joules per gram per degree, which equals about 10 degrees.

Correct answer: Nothing, Kc is always unitless in AP chemistry

Unitless is the correct answer. In AP chemistry equilibrium constants are treated as dimensionless because each concentration or pressure term is divided by a standard reference state, so no units are reported.

Correct answer: It becomes K squared

K squared is the correct answer. Multiplying every coefficient by a factor n raises the equilibrium constant to the nth power, so doubling all coefficients squares the original K.

Correct answer: The product of the two individual constants

The product of the two constants is the correct answer. When reactions are added to obtain an overall reaction, their equilibrium constants are multiplied together to give the overall constant.

Correct answer: The reaction shifts in reverse to form more reactant

Shifts in reverse is the correct answer. When Q exceeds K there is too much product relative to equilibrium, so the net reaction proceeds backward, converting product to reactant until Q equals K.

Correct answer: Ksp equals s squared

Ksp equals s squared is the correct answer. For a salt producing one cation and one anion each at concentration s, the solubility product is the product of the two ion concentrations, which is s times s, or s squared.

Correct answer: The equilibrium constant is very small relative to the initial concentration

Very small K relative to initial concentration is the correct answer. When K is small, the change x is tiny compared with the initial concentration, so subtracting x can be neglected to simplify the algebra.

Correct answer: Not shift, because both sides have equal moles of gas

Not shift is the correct answer. A volume change only shifts equilibrium when the two sides differ in moles of gas, so with equal moles on each side the position is unaffected.

Correct answer: The product RT, the gas constant times absolute temperature

RT is the correct answer. Kp equals Kc times the quantity RT raised to the change in moles of gas, where R is the gas constant and T is the absolute temperature.

Correct answer: They are equal

They are equal is the correct answer. When the moles of gas do not change, the factor RT is raised to the zero power, which equals one, making Kp and Kc numerically identical.

Correct answer: Q greater than Ksp

Q greater than Ksp is the correct answer. When the calculated ion product exceeds the solubility product, the solution is supersaturated and a precipitate forms until Q falls back to Ksp.

Correct answer: Exactly saturated and at equilibrium

Exactly saturated and at equilibrium is the correct answer. When the ion product equals the solubility product, the dissolved ions are in equilibrium with the solid, defining a saturated solution.

Correct answer: K increases

K increases is the correct answer. For an endothermic reaction, raising the temperature favors product formation, which increases the value of the equilibrium constant.

Correct answer: Temperature

Temperature is the correct answer. Changes in concentration, pressure, or catalyst shift the position of equilibrium but only a change in temperature alters the value of the equilibrium constant itself.

Correct answer: The partial pressure of carbon dioxide

The partial pressure of carbon dioxide is the correct answer. Pure solids are excluded from the expression, so only the gaseous carbon dioxide term remains in the equilibrium constant.

Correct answer: The mixture is already at equilibrium and will not shift

Already at equilibrium is the correct answer. When Q equals K, the concentrations already satisfy the equilibrium condition, so there is no net shift in either direction.

Correct answer: Le Chatelier's principle

Le Chatelier's principle is the correct answer. The principle states that a system at equilibrium responds to a stress by shifting to partially counteract that stress, which underlies the resistance to change.

Correct answer: Increasing the total pressure by decreasing volume

Increasing pressure by decreasing volume is the correct answer. The product ammonia side has fewer moles of gas, so raising pressure shifts the equilibrium toward the side with fewer gas moles, producing more ammonia.

Correct answer: The solution becomes saturated and dissolution equals precipitation

Saturated with dissolution equal to precipitation is the correct answer. At saturation the rate of ions leaving the solid equals the rate of ions rejoining it, so no net change is observed though both processes continue.

Correct answer: Q decreases

Q decreases is the correct answer. Increasing a reactant concentration enlarges the denominator of the reaction quotient, which lowers Q below K and drives the reaction forward.

Correct answer: Far to the right toward products

Far to the right toward products is the correct answer. A Kc much larger than one means product concentrations greatly exceed reactant concentrations at equilibrium, placing the position toward the products.

Correct answer: It does not alter the partial pressures or concentrations of the reacting gases

It does not alter partial pressures or concentrations is the correct answer. At constant volume the noble gas raises total pressure but the individual concentrations and partial pressures of the reacting species stay the same, so Q is unchanged.

Correct answer: The concentration of the pure liquid water solvent

The pure liquid water solvent is the correct answer. In dilute aqueous solutions the concentration of the water solvent is essentially constant, so it is omitted from the equilibrium constant expression.

Correct answer: Ammonia

Ammonia is the correct answer. Ammonia accepts a proton from water to form the ammonium ion, so by the Bronsted-Lowry definition ammonia is the proton acceptor and therefore the base.

Correct answer: Ammonium ion and ammonia

Ammonium ion and ammonia is the correct answer. The ammonium ion and ammonia differ by a single hydrogen ion, so they form a true conjugate acid-base pair, with the ammonium ion as the acid.

Correct answer: Readily gives up its proton, leaving a base with little tendency to reaccept it

Readily gives up its proton is the correct answer. Because a strong acid donates its proton almost completely, the resulting conjugate base has very little attraction for protons and is therefore weak.

Correct answer: $1.0 \times 10^{-5}$ molar

$1.0 \times 10^{-5}$ molar is the correct answer. Because pH is the negative logarithm of the hydrogen ion concentration, a pH of 5 corresponds to a hydrogen ion concentration of $10^{-5}$.

Correct answer: 11

11 is the correct answer. The pOH equals the negative logarithm of the hydroxide concentration, which is 3, and subtracting 3 from 14 gives a pH of 11.

Correct answer: 5

5 is the correct answer. pKa is the negative logarithm of Ka, so the negative logarithm of $10^{-5}$ equals 5.

Correct answer: An acid with Ka of $7.5 \times 10^{-3}$

The acid with Ka of $7.5 \times 10^{-3}$ is the correct answer. A larger Ka indicates more complete ionization, and among the choices this value is the largest, so that acid is the strongest.

Correct answer: A ratio of one to one

A ratio of one to one is the correct answer. When the conjugate base and weak acid are present in equal amounts, the logarithm term in the Henderson-Hasselbalch equation is zero, so the pH equals the pKa.

Correct answer: One unit above the pKa

One unit above the pKa is the correct answer. The logarithm of a ten to one ratio of base to acid equals one, so the Henderson-Hasselbalch equation gives a pH that is one unit higher than the pKa.

Correct answer: Buffer region

Buffer region is the correct answer. Before the equivalence point the solution contains both the weak acid and its conjugate base, forming a buffer that resists pH change and produces a gently sloping section of the curve.

Correct answer: Low

Low is the correct answer. Before any base is added the solution contains only the strong acid, so the hydrogen ion concentration is high and the pH is low.

Correct answer: 0.50 mol

0.50 mol is the correct answer. A monoprotic acid donates one proton per molecule, so neutralizing 0.50 mol of the acid requires an equal 0.50 mol of hydroxide ion in a one to one reaction.

Correct answer: 0.100 molar

0.100 molar is the correct answer. Equal volumes and a one to one mole ratio mean the acid and base concentrations are equal, so the acid concentration matches the base at 0.100 molar.

Correct answer: Its transition range matches the equivalence point pH, which is above 7

Its transition range matches the equivalence point pH is the correct answer. A weak acid titrated with a strong base has an equivalence point above 7, so an indicator like phenolphthalein that changes near pH 8 to 10 signals the endpoint accurately.

Correct answer: Hydronium ions and hydroxide ions

Hydronium ions and hydroxide ions is the correct answer. In autoionization one water molecule transfers a proton to another, generating a hydronium ion and a hydroxide ion in equal amounts.

Correct answer: $1.0 \times 10^{-13}$ molar

$1.0 \times 10^{-13}$ molar is the correct answer. The hydrogen ion concentration is 0.10 molar, and dividing the ion product of water by this value gives a hydroxide concentration of about $10^{-13}$.

Correct answer: The added oxygens pull electron density away, weakening the oxygen-hydrogen bond

The added oxygens pull electron density away is the correct answer. Additional electronegative oxygen atoms draw electron density from the oxygen-hydrogen bond, weakening it so the proton is released more easily and the acid is stronger.

Correct answer: The weaker hydrogen-iodine bond, which breaks more easily

The weaker hydrogen-iodine bond is the correct answer. The larger iodine atom forms a longer, weaker bond to hydrogen than fluorine does, so hydroiodic acid releases its proton more readily and is the stronger acid.

Correct answer: The pH stays nearly the same because the ratio of base to acid is unchanged

The pH stays nearly the same is the correct answer. Diluting a buffer changes both the conjugate base and weak acid concentrations by the same factor, so their ratio and therefore the pH remain nearly constant, although buffer capacity drops.

Correct answer: Hydrochloric acid and sodium chloride

Hydrochloric acid and sodium chloride is the correct answer. A buffer requires a weak acid and its conjugate base, but hydrochloric acid is a strong acid and chloride is its essentially nonbasic conjugate, so this pair cannot buffer.

Correct answer: The fraction of acid molecules that dissociate into ions

The fraction of acid molecules that dissociate is the correct answer. Percent ionization expresses the ratio of ionized acid to the original acid concentration as a percentage, indicating how completely the weak acid dissociates.

Correct answer: The hydrogen ion concentration equals $\sqrt{K_a \times \text{initial acid concentration}}$

$\sqrt{K_a \times \text{initial concentration}}$ is the correct answer. For a weak acid with small ionization, the equilibrium expression simplifies so the hydrogen ion concentration approximately equals $\sqrt{K_a \times \text{initial acid concentration}}$.

Correct answer: The excess hydroxide ions from the added base

The excess hydroxide ions is the correct answer. After the equivalence point all the acid is neutralized, so the leftover hydroxide from the added strong base determines the high pH.

Correct answer: Two

Two is the correct answer. A diprotic acid has two ionizable protons that are neutralized in two successive steps, so its titration curve shows two distinct equivalence points.

Correct answer: The weak acid component reacts with the added base to limit the pH increase

The weak acid component reacts with the added base is the correct answer. When base is added, the weak acid in the buffer neutralizes most of it, converting to conjugate base and keeping the pH change small.

Correct answer: The moles of added titrant equal the moles needed to react with all the analyte

The moles of titrant equal the moles needed to react with all the analyte is the correct answer. The equivalence point is defined by stoichiometric completion of the reaction, regardless of whether the resulting pH is acidic, neutral, or basic.

Correct answer: The carbonate ion accepts protons from water, releasing hydroxide ions

The carbonate ion accepts protons from water is the correct answer. As the conjugate base of a weak acid, the carbonate ion hydrolyzes by taking protons from water, generating hydroxide ions and making the solution basic.

Correct answer: Sodium chloride

Sodium chloride is the correct answer. Both the sodium ion and the chloride ion come from a strong base and a strong acid respectively, so neither hydrolyzes appreciably and the solution remains nearly neutral.

Correct answer: Increases

Increases is the correct answer. Diluting a weak acid shifts the ionization equilibrium toward more dissociation, so even though the hydrogen ion concentration falls, the percent of acid molecules that ionize increases.

Correct answer: $1.0 \times 10^{-7}$ molar

$1.0 \times 10^{-7}$ molar is the correct answer. In a neutral solution the hydronium and hydroxide concentrations are equal, and since their product is $10^{-14}$, each must be $10^{-7}$.

Correct answer: Acidic

Acidic is the correct answer. A pOH of 9 corresponds to a pH of 5, and since the pH is below 7 the solution is acidic.

Correct answer: Higher concentrations of the weak acid and conjugate base

Higher concentrations of the weak acid and conjugate base is the correct answer. A buffer with greater concentrations of both components can neutralize larger amounts of added acid or base before the pH changes significantly, giving it a higher capacity.

Correct answer: Donates a pair of electrons

Donates a pair of electrons is the correct answer. The Lewis model defines a base as an electron-pair donor, a broader definition than the Bronsted-Lowry proton acceptor.

Correct answer: Accepts a pair of electrons to form a bond

Accepts a pair of electrons is the correct answer. A Lewis acid is an electron-pair acceptor that forms a coordinate covalent bond with the electron pair supplied by the Lewis base.

Correct answer: 0

0 is the correct answer. Complete dissociation gives a hydrogen ion concentration of 1.0 molar, and the negative logarithm of 1 is 0.

Correct answer: The conjugate acid of the weak base remains and lowers the pH

The conjugate acid of the weak base remains is the correct answer. At the equivalence point the weak base has been converted to its conjugate acid, which donates protons to water and lowers the pH below 7.

Correct answer: $1.0 \times 10^{-9}$

$1.0 \times 10^{-9}$ is the correct answer. Since Ka times Kb equals the ion product of water, dividing $10^{-14}$ by the Ka of $10^{-5}$ yields a Kb of $10^{-9}$.

Correct answer: It has a measurable but incomplete degree of ionization, giving a higher pH than expected for full dissociation

Incomplete ionization giving a higher pH is the correct answer. A weak acid only partially dissociates, so at the same concentration it produces fewer hydrogen ions and a higher pH than a fully dissociating strong acid would.

Correct answer: Neutral

Neutral is the correct answer. Equal moles of a strong acid and a strong base react completely to form water and a salt that does not affect pH, so the mixture is neutral.

Correct answer: Positive

Positive is the correct answer. Producing more moles of gas increases the dispersal of matter and the number of accessible microstates, so the standard entropy change is positive.

Correct answer: A perfect crystalline solid at absolute zero

A perfect crystalline solid at absolute zero is the correct answer. The third law of thermodynamics sets the entropy of a perfect crystal at absolute zero to zero, providing the baseline for absolute entropy values.

Correct answer: Enthalpically favorable

Enthalpically favorable is the correct answer. A large negative enthalpy change releases energy and makes the process enthalpically favorable, contributing a negative term to the free energy change.

Correct answer: It must be positive

It must be positive is the correct answer. When enthalpy is unfavorable, a positive entropy change allows the temperature-entropy term to eventually overcome it, making the reaction favorable above a threshold temperature.

Correct answer: Zero

Zero is the correct answer. At the crossover temperature the free energy change equals zero, so setting the Gibbs expression to zero and solving gives the temperature where favorability reverses.

Correct answer: Exactly zero volts

Exactly zero volts is the correct answer. The standard hydrogen electrode is defined as the reference half-cell with a standard reduction potential of zero volts, against which all other potentials are measured.

Correct answer: The cathode reduction potential

The cathode reduction potential is the correct answer. The standard cell potential equals the cathode reduction potential minus the anode reduction potential, using both values as reduction potentials.

Correct answer: Be oxidized at the anode

Be oxidized at the anode is the correct answer. The species with the more negative reduction potential is more easily oxidized, so it serves as the anode where oxidation occurs.

Correct answer: Becomes more negative

Becomes more negative is the correct answer. The free energy change is the negative product of the number of electrons, Faraday's constant, and the cell potential, so a larger positive potential gives a more negative free energy change.

Correct answer: The negative terminal

The negative terminal is the correct answer. In an electrolytic cell the external power source pushes electrons to the cathode, so the cathode is connected to the negative terminal where reduction is forced to occur.

Correct answer: Faraday's constant

Faraday's constant is the correct answer. Faraday's constant gives the magnitude of electric charge per mole of electrons and is used to convert between charge and moles of electrons in electrochemistry.

Correct answer: The elapsed time

The elapsed time is the correct answer. Total charge equals current multiplied by the time the current flows, which is the first step in stoichiometric electrolysis calculations.

Correct answer: The cathode

The cathode is the correct answer. In electroplating, metal ions are reduced and deposited onto the object, which therefore acts as the cathode where reduction takes place.

Correct answer: Increases it above the standard value

Increases it above the standard value is the correct answer. By the Nernst relationship, raising reactant concentrations relative to products shifts the cell potential to a value higher than the standard cell potential.

Correct answer: Zero

Zero is the correct answer. At equilibrium there is no net driving force for electron flow, so the measured cell potential of the dead cell is zero.

Correct answer: Greater than one

Greater than one is the correct answer. A negative standard free energy change favors products at equilibrium, which corresponds to an equilibrium constant greater than one.

Correct answer: It increases

It increases is the correct answer. Sublimation converts a highly ordered solid into a widely dispersed gas, greatly increasing the number of microstates and the entropy.

Correct answer: Become dispersed throughout the solution

Become dispersed throughout the solution is the correct answer. Dissolution breaks the ordered crystal and spreads ions through the solvent, increasing the dispersal of matter and the entropy.

Correct answer: The reaction rate

The reaction rate is the correct answer. Thermodynamic favorability indicates whether a reaction can occur, but kinetics, not free energy, governs how fast it actually proceeds.

Correct answer: Decreases over time

Decreases over time is the correct answer. Oxidation at the anode converts metal atoms into ions that enter solution, so the anode loses mass as the cell discharges.

Correct answer: Zero

Zero is the correct answer. When the reaction quotient equals the equilibrium constant the system is at equilibrium, and the Nernst equation yields a cell potential of zero.

Correct answer: Sufficiently high

Sufficiently high is the correct answer. With a positive enthalpy change opposing favorability, a high enough temperature makes the positive temperature-entropy term dominate, giving a negative free energy change.