AP Chemistry Question 359: Answer and Explanation

Test Information

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Question: 359

11. If the concentration of Mg2+ is changed from 1.0 M to 0.1 M in the galvanic cells above, what will happen to the observed cell voltages in galvanic cells 2 and 3?

  • A. The voltage in both galvanic cells 2 and 3 will increase.
  • B. The voltage will decrease in both galvanic cells 2 and 3.
  • C. The voltage in galvanic cell 2 will increase and will decrease in galvanic cell 3.
  • D. The voltage in galvanic cell 3 will increase and will decrease in galvanic cell 2.

Correct Answer: A

Explanation:

(A) As discussed in Example 13.6 and the Solution for Exercise 13.5, if E°cell is positive and the product concentration is larger than the reactant concentration, the voltage will decrease toward zero. In this case the product concentration is less than the reactant concentration, so the voltage will increase. This will happen in both cells 2 and 3.