MCAT General Chemistry Freestanding Practice Questions: Electrochemistry

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1. Typical dry cell batteries contain a zinc anode and a carbon cathode and produce a potential difference of 1.5 V. Given that many electronic devices require additional voltage, which of the following would result in an overall increase in voltage?

I. Doubling the quantity of Zn(s)

II. Placing two batteries in parallel

III. Replacing Zn(s) with Na(s)

  • A. I only
  • B. III only
  • C. I and II only
  • D. II and III only

2. Given the following reactions:

Pb2+ + 2e- → Pb(s) Eº = –0.13 V
Fe(s) → Fe2+ + 2e- Eº = 0.45 V

Which one of the following is true?

  • A. Pb(s) is a better reductant than Fe(s)
  • B. Fe(s) is a worse reductant than Pb(s)
  • C. Fe2+ is a better oxidant than Pb2+
  • D. Pb2+ is a better oxidant than Fe2+

3. Which of the following best characterizes the spontaneous half-reaction below under standard conditions?

Pd2+ + 2e- → Pd

  • A. ∆G° > 0 and E° < 0
  • B. ∆G° < 0 and E° < 0
  • C. ∆G° > 0 and E° > 0
  • D. ∆G° < 0 and E° > 0

4. High valent metals (those with large, positive oxidation states) are often used as strong oxidizing agents. Which of the following compounds would have the most positive reduction potential vs. a standard hydrogen electrode?

  • A. FeCl3
  • B. OsO4
  • C. Zn(NO3)Cl
  • D. W(CO)6

5. Which of the following best describes the difference between a galvanic cell and an electrolytic cell?

  • A. In a galvanic cell, the anode is the site of oxidation, whereas in an electrolytic cell the anode is the site of reduction.
  • B. In a galvanic cell, the cathode is the negative electrode, whereas in an electrolytic cell the cathode is the positive electrode.
  • C. In a galvanic cell, spontaneous reactions generate a current, whereas in an electrolytic cell a current forces nonspontaneous reactions to occur.
  • D. In a galvanic cell, the electrons flow from anode to cathode, whereas in an electrolytic cell the electrons flow from cathode to anode.

6. To give "white gold" a white appearance, it is plated with rhodium by immersion in a rhodium sulfate solution (Rh2(SO4)3(aq)). Provided with a current of 2.0 A, how long must a 3.0 g white gold broach be immersed to plate 3.0 × 10-5 g of rhodium? (Faraday's constant = 96,500 C/mol e-)

  • A. 0.0009 s
  • B. 0.0098 s
  • C. 0.042 s
  • D. 0.56 s

7. A galvanic cell is constructed from two half-cells of platinum and iron. The half-reactions for these two elements are provided as follows:

Pt2+(aq) + 2e- → Pt (s)E° = +1.20 V
Fe3+(aq) + 3e- → Fe (s)E° = –0.036 V

Which of the following statements is true about the galvanic cell?

  • A. E° = 1.164 V, and Pt2+ is the reducing agent
  • B. E° = 1.164 V, and Fe3+ is the reducing agent.
  • C. E° = 1.236 V, and Pt2+ is the oxidizing agent.
  • D. E° = 1.236 V, and Fe3+ is the oxidizing agent.

8. An electrochemical cell is constructed using two inert electrodes in one chamber with an inert electrolyte. The binary compound ICl is dissolved in the electrolyte, current is applied, and I2 and Cl2 are produced. Which of the following statements is true?

  • A. Cl2 was produced by reduction at the cathode.
  • B. I2 was produced by oxidation at the cathode.
  • C. Cl2 was produced by oxidation at the cathode.
  • D. I2 was produced by reduction at the cathode.