MCAT General Chemistry Question 244: Answer and Explanation

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Question: 244

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

Correct Answer: C

Explanation:

C Since current (I) = charge(Q) / time(t) we can set up and solve the following equation keeping in mind that the rhodium reduction in question is Rh³⁺ + 3e^- → Rh(s).

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