AP Chem Final

After a certain pesticide compound is applied to crops, its decomposition is a first-order reaction with a half-life of 56 days. What is the rate constant, k, for the decomposition reaction? a. 0.012 day^-1 b. 0.018 day^-1 c. 56 day^-1 d. 81 day^-1

a.

Ge(g)+2Cl2(g)⇄GeCl4(g) The value of the equilibrium constant for the reaction represented above is 1×1010. What is the value of the equilibrium constant for the following reaction? 2GeCl4(g)⇄2Ge(g)+4Cl2(g) a. 1×10^−20 b. 1×10^−10 c. 1×10^10 d. 1×10^20

a.

Which compound, chloroacetic acid or iodoacetic acid, most likely has the lower boiling point, and why? a. Chloroacetic acid, because the London dispersion forces among its molecules are weaker. b. Chloroacetic acid, because the dipole-dipole forces among its molecules are weaker. c. Iodoacetic acid, because the London dispersion forces among its molecules are stronger. d. Iodoacetic acid, because the dipole-dipole forces among its molecules are stronger.

a.

Which of the following statements is true about sodium glycinate, represented above? a. It is an ionic solid at room temperature. b. It is not soluble in water. c. It evaporates easily because of the lack of hydrogen bonding. d. It dissolves in water to form an acidic solution.

a.

A sealed 10.0 L flask at 400 K contains equimolar amounts of ethane and propanol in gaseous form. Which of the following statements concerning the average molecular speed of ethane and propanol is true? a. The average molecular speed of ethane is less than the average molecular speed of propanol. b. The average molecular speed of ethane is greater than the average molecular speed of propanol. c. The average molecular speed of ethane is equal to the average molecular speed of propanol. d. The average molecular speeds of ethane and propanol cannot be compared without knowing the total pressure of the gas mixture.

b.

A solution is prepared by mixing equal volumes of 0.20 M HC3H3O2 and 0.40 M NaC2H3O2. Which of the following correctly describes what occurs if a small amount of HCl(aq) or NaOH(aq) is added? a. If HCl(aq) is added, the pH will increase only slightly because Cl- ions will react with C2H3O2- ions. b. If HCl(aq) is added, the pH will decrease only slightly because H+ ions will react with C2H3O2- ions. c. If NaOH(aq) is added, the pH will increase only slightly because the OH- ions will react with C2H3O2- ions. d. If NaOH(aq) is added, the pH will decrease only slightly because OH-ions will react with HC3H3O2 molecules.

b.

An aqueous solution contains small but equal concentrations of both chloroacetic and fluoroacetic acids. Which statement comparing the percent ionizations of the two acids in the solution is true? a. The percent ionization of chloroacetic acid is greater than that of fluoroacetic acid. b. The percent ionization of chloroacetic acid is less than that of fluoroacetic acid. c. The percent ionizations cannot be compared without knowing the concentrations of the two acids. d. The percent ionizations cannot be compared without knowing the pH of the solution.

b.

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0 M HCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibration line below. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table below. Which of the following equations best represents te species that react and the species that are produced when CaCO3(s) and HCl(aq) are combined? a. 2H+(aq) + CaCO3(s) --> Ca^2+(aq) + CO3^2-(aq) + H2(g) b. 2H+(aq) + CaCO3(s) --> Ca^2+(aq) + H2O(l) + CO2(g) c. 2H+(aq) + CaCO3(s) --> Ca^2+(aq) + 2OH-(aq) + CO(g) d. 2HCl(aq) + CaCO3(s) --> Ca^2+(aq) + H2O(l) + CO2(g) + 2Cl-(aq)

b.

C9H8O4(aq) + NaOH(aq) ⇄ C9H7O4-(aq) + Na+(aq) + H20(l) The reaction represented above occurs when 2.00x10^-4 mole of pure acetylsalicylic acid, C9H8O4, is completely dissolved in 15.00 mL of water in a flask and titrated to the equivalence point with 0.100 M NaOH(aq). Which of the following statements about the titration is true at the equivalence point? a. [C9H8O4] is greater than [C9H7O4-]. b. [C9H8O4] is less than [C9H7O4-]. c. [C9H8O4] is equal to [C9H7O4-]. d. The relationship between [C9H8O4] and [C9H7O4-] cannot be determined without additional information.

b.

CaF2(s)⇄Ca2+(aq)+2F−(aq) Ksp=4.0×10−11 The concentration of F−(aq) in drinking water that is considered to be ideal for promoting dental health is 4.0×10^−5M. Based on the information above, the maximum concentration of Ca2+(aq) that can be present in drinking water without lowering the concentration of F−(aq) below the ideal level is closest to a. 0.25M d. 0.025M c. 1.6×10−6M d. 1.6×10−15M

b.

Of the three solutions listed in the table above, which one, if any, has the greatest electrical conductivity and why? a. 0.1 M HC2H3O2 (aq) because its molecules have the most atoms. b. 0.1 M KI (aq) because KI completely dissociates in water to produce ions. c. 0.1 M CH3OH (aq) because its molecules can form hydrogen bonds. d. All three solutions have the same electrical conductivity because the concentration are the same.

b.

The diagram above represents a particle in aqueous solution. Which of the following statements about the particle is correct? a. The particle must be a cation because the negative end of each water molecule is pointed toward it. b. The particle must be an anion because the positive end of each water molecule is pointed toward it. c. The charge of the particle cannot be determined because water molecules have no net charge. d. The charge of the particle cannot be determined because the water molecules are arranged symmetrically and their partial charges cancel.

b.

The first five ionization energies of an unknown element are listed in the table above. Which of the following statements correctly identifies the element and cites the evidence supporting the identification? a. Na, because of the large difference between the first and the second ionization energies b. Al, because of the large difference between the third and fourth ionization energies c. Si, because the fifth ionization energy has the greatest value d. P, because a neutral atom of P has five valence electrons

b.

The structural formula of the glycinium cation is shown above. Arrows indicate the pKa values for the labile protons in the molecule. Which of the following is true about the geometry of the glycinium cation? a. The leftmost C atom and all the atoms directly bonded to it lie in the same plane. b. Both C atoms and both O atoms lie in the same plane. c. The N-C-C bond angle is 180°. d. The geometry around the N atom is planar.

b.

To catalyze a biochemical reaction, an enzyme typically a. drives the reaction to completion by consuming byproducts of the reaction b. binds temporarily to reactant molecules to lower the activation energy of the reaction c. dissociates into additional reactant molecules, thereby increasing the reaction rate d. decomposes and releases energy to increase the number of successful collisions between reactant molecules

b.

Which of the following can be inferred from the diagram above that shows the dependence of potential energy on the internuclear distance between two atoms? a. The atoms form a bond with a bond length of 25 pm. b. The atoms form a bond with a bond length of 75 pm. c. The net force between the atoms is attractive at 25 pm. d. The net force between the atoms is attractive at 75 pm.

b.

A student titrates 10.0mL samples of 1.0M solutions of each of the haloacetic acids with a standard solution of NaOH. Which of the following statements correctly predicts the volume of NaOH(aq) needed to reach the equivalence point? a. Fluoroacetic acid will need the smallest volume of NaOH(aq) to reach the equivalence point. b. Iodoacetic acid will need the smallest volume of N a O H, aqueous to reach the equivalence point. c. All of the acids will need the same volume of N a O H, aqueous to reach the equivalence point. d. All of the haloacetic acids are weak; therefore none will reach an equivalence point.

c.

In an experiment, 30.0 g of ethane and 30.0 g of propanol are placed in separate reaction vessels. Each compound undergoes complete combustion with excess O2(g). Which of the following best compares the quantity of heat released in each combustion reaction? a. qethane < qpropanol b. qethane = qpropanol c. qethane > qpropanol d. The quantities of heat released in the combustion of ethane and propanol cannot be compared without knowing the specific heat capacity of the compounds.

c.

Samples of NaF(s) and NH4Cl(s) are dissolved in separate beakers that each contain 100mLof water. One of the salts produces a slightly acidic solution. Which of the following equations best represents the formation of the slightly acidic solution? a. Na+(aq)+2H2O(l)⇄NaOH(aq)+H3O+(aq) b. F−(aq)+H2O(l)⇄HF(aq)+OH−(aq) c. NH4+(aq)+H2O(l)⇄NH3(aq)+H3O+(aq) d. Cl−(aq)+H2O(l)⇄HCl(aq)+OH−(aq)

c.

Solid carbon tetrachloride, CCl4(s), is represented by the diagram above. The attractions between the CCl4 molecules that hold the molecule together in the solid state are best identified as a. polar covalent bonds b. nonpolar covalent bonds c. intermolecular attractions resulting from temporary dipoles d. intermolecular attractions resulting from permanent dipoles.

c.

The structural formula of the glycinium cation is shown above. Arrows indicate the pKa values for the labile protons in the molecule. What is the approximate H−O−C bond angle in the glycinium cation? a. 180° b. 120° c. 105° d. 90°

c.

Which of the following is a list of the minimum amount of data needed for determining the molar enthalpy of solution of KCl(s) in pure H2O(l)? (Assume that the KCl(aq) has the same specific heat capacity as pure water and that the initial temperatures of the KCl(s) and the water are the same.) a. Mass of KCl(s), initial temperature of the water, and final temperature of the solution b. Mass of H2O, initial temperature of the water, and final temperature of the solution c. Mass of KCl(s), mass of H2O, initial temperature of the water, and final temperature of the solution d. Mass of KCl(s), mass of H2O, initial temperature of the water, final temperature of the solution, and atmospheric pressure

c.

2 FeO(s)⇄2 Fe(s)+O2(g) Keq=1×10^−6 at 1000K CO2(g)⇄C(s)+O2(g) Keq=1×10^−32 at 1000K The formation of Fe(s) and O2(g) from FeO(s) is not thermodynamically favorable at room temperature. In an effort to make the process favorable, C(s) is added to the FeO(s) at elevated temperatures. Based on the information above, which of the following gives the value of Keq and the sign of ΔG° for the reaction represented by the equation below at 1000K? 2 FeO(s)+C(s)⇄2 Fe(s)+CO2(g) a. Keq: 1×10^−38 ΔG°: Positive b. Keq: 1×10^−38 ΔG°: Negative c. Keq: 1×10^26 ΔG°: Positive d. Keq: 1×10^26 ΔG°: Negative

d.

A 1.0 mol sample of He(g) at 25C is mixed with a 1.0 mol sample of Xe(g) at 50C. Which of the following correctly predicts the changes in average kinetic energy and the average speed of the atoms that will occur as the mixture approaches thermal equilibrium? a. Average Kinetic Energy of Xe Atoms: Will increase Average Speed of Xe Atoms: Will increase b. Average Kinetic Energy of Xe Atoms: Will increase Average Speed of Xe Atoms: Will decrease c. Average Kinetic Energy of Xe Atoms: Will decrease Average Speed of Xe Atoms: Will increase d. Average Kinetic Energy of Xe Atoms: Will decrease Average Speed of Xe Atoms: Will decrease

d.

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0 M HCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibration line below. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table below. The mass percent of CaCO3(s) in the eggshell sample is closest to a. 30% b. 45% c. 60% d. 75%

d.

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0 M HCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibration line below. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table below. Which of the following modifications will increase the rate of the reaction the most? a. Using 2.0 M CH3COOH(aq) instead of 2.0 M HCl(aq) b. Cooling the HCl(sq) to a lower temperature than it was in the original experiment c. Reducing the volume of the reaction vessel d. Using eggshells that are more finely powdered than those used in the original experiment

d.

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0 M HCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibration line below. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table below. Another sample of eggshell reacts completely with 4.0 mL of an HCl(aq) solution of unknown concentration. If the reaction produced 0.095 atm of gas, the concentration of the HCl(aq) solution was at least a. 0.0020 M b. 0.050 M c. 0.50 M d. 1.0 M

d.

CO2(g)+2LiOH(s)→Li2CO3(aq)+H2O(l) In a one-person spacecraft, an astronaut exhales 880g of CO2(g) (molar mass 44g/mol) per day. To prevent the buildup of CO2(g) in the spacecraft, a device containing LiOH(s) is used to remove the CO2(g), as represented by the equation above. What mass of LiOH(s) (molar mass 24g/mol) is needed to react with all of the CO2(g) produced by an astronaut in one day? a. 40.g b. 240g c. 480g d. 960g

d.

The saturated CuSO4(aq) shown above is left uncovered on a lab bench at a constant temperature. As the solution evaporates, 1.0mL samples of the solution are removed every three days and the [SO42−] in the samples is measured. It is observed that the [SO42−] in the solution did not change over time. Which of the following best helps to explain the observation? a. As the solution evaporates, Cu2+(aq) and SO42−(aq)leave the beaker along with the water molecules. b. As the solution evaporates, the dissolution of CuSO4(s) in the beaker decreases. c. The evaporation of water is endothermic, so more CuSO4(s) dissolves exothermically in the solution, which increases the [SO42−]. d. As water evaporates, more CuSO4(s) precipitates out of the solution in the beaker.

d.

The structural formulas for two isomers of 1.2-dichloroethene are shown above. Which of the two liquids has the higher equilibrium vapor pressure at 20°C, and why? a. The cis-isomer, because it has dipole-dipole interactions, whereas the trans-isomer has only London dispersion forces b. The cis-isomer, because it has only London dispersion forces, whereas the trans-isomer also has dipole-dipole interactions c. The trans-isomer, because it has dipole-dipole interactions, whereas the cis-isomer has only London dispersion forces d. The trans-isomer, because it has only London dispersion forces, whereas the cis-isomer also has dipole-dipole interactions

d.

Which of the following best explains why the combustion reactions represented in the table are exothermic? a. The number of bonds in the reactant molecules is greater than the number of bonds in the product molecules. b. The number of bonds in the reactant molecules is less than the number of bonds in the product molecules. c. The energy required to break the bonds in the reactants is greater than the energy released in forming the bonds in the products. d. The energy required to break the bonds in the reactants is less than the energy released in forming the bonds in the products.

d.

Which of the following is the molecular formula of the unknown compound? a. C4H8 b. C4H8O c. C4H4O2 d. C4H8O2

d.

based on the structural formulas, which of the following identifies the compound that is more soluble in water and best helps to explain why? a. Ethane, because the electron clouds of its molecules are more polarizable than those of propanol. b. Ethane, because its molecules can fit into the spaces between water molecules more easily than those of propanol can. c. Propanol, because its molecules have a greater mass than the molecules of ethane have. d. Propanol, because its molecules can form hydrogen bonds and with water molecules but those of ethane cannot.

d.