MCAT General Chemistry Practice Test 9: Electrochemistry

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A student follows the schematic below and sets up the following electrochemical cell at room temperature.

Figure 1 Schematic of an experimental electrochemical cell

The student fills Beaker X with a 0.01 M solution of CuSO4 and Beaker Y with a 1 M solution of CuSO4. Two copper plates serve as electrodes and a KCl(aq) salt bridge is used. Because of the nonstandard conditions, the student uses the Nernst equation to calculate the expected potential of the cell:

where E° is the standard cell voltage, R is the universal gas constant, T is the absolute temperature, n is the number of electron moles, F is Faraday's constant, and Q is the reaction quotient. Substituting in the constant variables and converting the natural logarithm, the student obtains the following formula:

After setting up the half-cells, the student connects the two electrodes via a voltmeter and measures the initial cell potential.

Table 1 Standard reduction potentials for copper ions

Half-ReactionE° (V)
Cu+ + e- → Cu(s)+ 0.52
Cu2+ + 2e- → Cu(s)+ 0.34

1. What is the standard cell voltage, E°, of the cell used in the experiment?

  • A. + 0.52 V
  • B. + 0.34 V
  • C. + 0.18 V
  • D. 0 V

2. Which of the following correctly describes the relationship between the movement of electrons and K+ ions?

  • A. K+ ions and electrons both travel towards Beaker X.
  • B. K+ ions travel towards Beaker X and electrons travel towards Beaker Y.
  • C. K+ ions travel towards Beaker Y and electrons travel towards Beaker X.
  • D. K+ ions and electrons both travel towards Beaker Y.

3. Which of the following substances has the atom with the greatest oxidation state?

  • A. CH2F2
  • B. K2O
  • C. S4O62--
  • D. Fe2O3

4. Which of the following best describes the cell used in the experiment?

  • A. Beaker X contains the cathode that is negatively charged.
  • B. Beaker Y contains the cathode that is negatively charged.
  • C. Beaker X contains the anode that is negatively charged.
  • D. Beaker Y contains the anode that is negatively charged.

5. What is the expected potential of the cell at the start of the experiment?

  • A. +0.118 V
  • B. +0.059 V
  • C. -0.118 V
  • D. -0.059 V