5 STEPS TO A 5: 500 AP Chemistry Questions to Know by Test Day! (2012)

362. The oxidation state most common to ions of Fe, Mn, and Zn in solution is:

(A) +1

(B) +2

(C) +3

(D) +4

(E) +5

363. The oxidation state of chlorine in HClO₄ is:

(A) –1

(B) +1

(C) +3

(D) +5

(E) +7

364. In which of the following species does chromium have the same oxidation number as in Cr₂O₄^2–?

(A) Cr₂(O₂CCH₃)₄

(B) Cr(CO)₆

(C) Cr₂O₇^2–

(D) K₃[Cr(O₂)4]

(E) Cr₂O₃

365. A 0.1-M solution of H₃PO₄ is a better conductor of electricity than a 0.1-M solution of NaCl. Which of the following best explains this observation?

(A) NaCl is less soluble than H₃PO₄.

(B) NaCl has a lower molar mass than H₃PO₄.

(C) H₃PO₄ dissociates to produce particles of a larger size than NaCl.

(D) H₃PO₄ is weakly acidic, which increases the flow of charge through a solution.

(E) Fewer moles of ions are present in the NaCl solution than in the same volume of an Na₃PO₄ solution.

366. Which of the following choices best explains why the reaction represented above generates electricity in a galvanic cell?

(A) Cl₂ is a stronger oxidizing agent than Br₂.

(B) Cl₂ loses electrons more easily than Br₂.

(C) Br atoms have more electrons than Cl atoms.

(D) Br₂ is more stable than Cl₂.

(E) Cl⁻ is more stable than Br⁻.

367. Which of the following statements is/are true regarding the reaction above?

I. Cu_(s) acts as an oxidizing agent.

II. H⁺_(aq) gets reduced.

III. The oxidation state of nitrogen changes from +5 to +2.

(A) I only

(B) II only

(C) III only

(D) II and III only

(E) I, II, and III

Questions 368 and 369 refer to a galvanic cell constructed of two half-cells and the two half-reactions represented below.

368. As the cell operates, which of the following species is contained in the half-cell containing the cathode?

I. Zn²⁺

II. Zn⁺

III. Ag⁺

(A) I only

(B) II only

(C) III only

(D) I and II only

(E) I and III only

369. What is the standard cell potential for this galvanic cell?

(A) –0.04 V

(B) 0.04 V

(C) 0.84 V

(D) 1.56 V

(E) 2.36 V

370. The photodecomposition of permanganate is shown above. As this reaction proceeds in the forward direction and the reaction species are considered from left to right, the oxidation number of Mn changes from:

(A) +1 to +2 and +2

(B) +5 to +2 and +2

(C) +5 to +6 and +4

(D) +7 to +6 and +4

(E) +7 to +2 and +2

Questions 371 and 372 refer to an electrolytic cell involving the following reaction.

371. Which of the following processes occurs in this reaction?

(A) O₃ acts as an oxidizing agent.

(B) O₃^6– acts as an oxidizing agent.

(C) Al³⁺ is reduced at the cathode.

(D) Al is oxidized at the anode.

(E) Aluminum is converted from a negative to a neutral oxidation state.

372. A steady current of 15 amperes is passed through the cell for 20 minutes. Which of the following correctly expresses how to calculate the number of grams of aluminum produced by this cell (1 faraday = 96,500 coulombs)?

373. According to the information above, what is the standard reduction potential for the half-reaction ?

(A) +0.67 V

(B) –0.67 V

(C) +1.47 V

(D) –1.47 V

(E) +3.07 V

374. An electric current of 1.00 ampere is passed through an aqueous solution of FeCl₃. Assuming 100 percent efficiency, how long will it take to electroplate exactly 1.00 mole of iron metal?

(1 faraday = 96,500 coulombs = 6.02 × 10²³ electrons)

(A) 32,200 sec

(B) 96,500 sec

(C) 193,000 sec

(D) 289,500 sec

(E) 386,000 sec

Questions 375–381 refer to a galvanic cell made of two half-cells. In one half-cell, a Zn electrode is bathed in a 1.0 M ZnSO₄ solution. The other cell contains a 1 M HCl solution and a hydrogen electrode.

375. Which of the following is the correct electron configuration for Zn²⁺?

(A) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

(B) 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰

(C) 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s²

(D) 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²

(E) 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹ 4s¹

376. Which of the following correctly identifies and justifies which species, Zn or Zn²⁺, has the highest ionization energy?

(A) Zn, electrons have a greater affinity for pure metals.

(B) Zn, it has a greater electron to proton ratio.

(C) Zn²⁺, it has a larger radius.

(D) Zn²⁺, it has a greater effective nuclear charge.

(E) Zn²⁺, it has a greater electron-to-proton ratio.

377. Processes that occur at the anode include which of the following?

I. Zn_(s) is oxidized to Zn²⁺_(aq).

II. Zn²⁺_(aq) is reduced to Zn_(s).

III. H_2(g) is oxidized to H⁺_(aq).

IV. 2 H⁺_(aq) is reduced to H_2(g).

(A) I only

(B) II only

(C) III only

(D) I and III only

(E) II and IV only

378. The salt bridge is filled with a saturated solution of KNO₃. Processes that occur at the salt bridge include which of the following?

I. K⁺ moves into the anode half-cell.

II. K⁺ moves into the cathode half-cell.

III. NO₃⁻ moves into the anode half-cell.

IV. NO₃⁻ moves into the cathode half-cell.

(A) I only

(B) III only

(C) I and IV only

(D) II and III only

(E) I, II, III, and IV

379. Which of the following is true regarding the HCl half-cell?

(A) The reduction of H⁺ to H₂ is neither spontaneous nor non-spontaneous.

(B) The reduction of H⁺ and oxidation of H₂ are at equilibrium.

(C) All electrochemical cells use a hydrogen half-cell.

(D) It is used to measure the reduction potential of Zn²⁺ because the reduction potential has a measured value of zero volts.

(E) The E° value of 0 V for the hydrogen half-cell is arbitrary.

380. Which of the following is true regarding the standard free energy change (ΔG°) of the cell?

(A) It is negative because the standard reduction potential of Zn²⁺ is negative.

(B) It is negative because the sum of the standard reduction potentials of Zn²⁺ and H⁺ is –0.76 V.

(C) It is negative because the oxidation of Zn is spontaneous.

(D) It is positive because the reduction of hydrogen ions is spontaneous.

(E) It has a value of zero because the reaction is at equilibrium.

381. Which of the following changes to the voltage, if any, would result from increasing the concentration of ZnSO₄?

(A) No change, the voltage of the cell is determined only by the standard reduction potentials of the electrodes.

(B) Increased voltage, the value of Q will fall below 1 and the log term in the Nernst equation will become more negative.

(C) Increased voltage, the reaction becomes more favorable as the concentration of Zn⁺ increases.

(D) Decreased voltage, the value of Q will fall below 1 and the log term in the Nernst equation will become more negative.

(E) Decreased voltage, the increased concentration of Zn²⁺ will inhibit the oxidation of Zn_(s).

382. Iron nails are often electroplated (galvanized) with zinc. Which of the following is true regarding this process (E° of Zn²⁺ → Zn_(s) = –0.76 V, E° of Fe²⁺ → Fe_(s) = –0.44 V)?

(A) Zn serves as a sacrificial anode for Fe.

(B) Zn serves as an airtight seal preventing the electrons from iron from reacting with oxygen.

(C) The galvanization process produces an alloy of Zn and Fe that is stronger and more resistant to oxidation than Fe alone.

(D) The galvanization process is spontaneous, thereby reducing the energy cost of producing nails.

(E) The oxidation of Zn allows the reduction of Fe²⁺ to proceed spontaneously.

383. Which of the following correctly relates the quantities needed for the conversion of chemical energy into electrical energy in a galvanic cell?

(A) The sum of the E° cell of the two half-cells.

(B) The product of the cell voltage and the total charge passed through the cell.

(C) The product of cell voltage and the natural log (ln) of K, the equilibrium constant for the redox reaction.

(D) The product of the gas constant and the voltage divided by the total charge passed through the cell.

(E) The difference between the voltages of the two half-cells.

384. All of the following statements are consistent with the operation of a galvanic cell except:

(A) During cell operation, reactant concentration and product formation decreases.

(B) The electrons that flow from anode to cathode are generated at the anode.

(C) E° values are specific for a particular reaction and do not vary with reactant concentration.

(D) At equilibrium, there is no net transfer of electrons and the cell cannot do work.

(E) As the product-to-reactant ratio increases, the work that can be done by the cell decreases.

Questions 385–387 refer to the following redox reaction that occurs in a lithium ion battery.

385. Which of the following reactions occurs at the anode?

386. All of the following are advantages of a lithium-ion battery except:

(A) Li⁺ has the most negative standard reduction potential.

(B) Fewer than 7-g Li are needed to provide 1-mol electron to the battery.

(C) Lithium is a powerful reducing agent.

(D) Lithium-ion batteries can be charged hundreds of times without deterioration.

(E) Lithium is a highly reactive metal that requires a nonaqueous electrolyte solution.

387. Features common to both galvanic and electrolytic cells include which of the following?

I. Oxidation at the anode

II. Can perform electrolysis

III. Spontaneous

(A) I only

(B) II only

(C) III only

(D) I and II only

(E) I, II, and III