Other Electrochemical Principles - MCAT Chemical and Physical Foundations of Biological Systems

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Question

A researcher is analyzing an electrolytic cell. In trial 1, he applies of current for two hours to the cell and observes that the cathode produces of zinc metal. In trial 2, he applies the same amount of current but only for one hour. What will the researcher observe in the cathode during trial 2?

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Answer

Faraday’s Law states that the amount of substance produced in a half-cell is dependent on the charge applied to the system; therefore, the more charge applied the more substance produced. The question states that the researcher applies the same amount of current, but for a shorter time, in trial 2. Recall the definition of current:

This means that charge equals:

Trial 1 and Trial 2 have the same current; however, trial 2 has a smaller time. This means that the charge applied in trial 2 is smaller than the charge applied in trial 1; therefore, according to Faraday’s law, the researcher must observe a smaller mass of zinc metal in trial 2.

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