A current of 2 A flows for 965 seconds through copper(II) sulphate solution. What mass of copper is deposited at the cathode? (1 Faraday = 96500 C, Cu = 64)
Answer and explanation
Correct answer: A. 0.64 g
- Step 1: Charge = current x time = 2 x 965 = 1930 C. Step 2. Moles of electrons = 1930 / 96500 = 0.02 mol. Step 3. Cu2+ needs 2 electrons, so moles of Cu = 0.01 mol and mass = 0.01 x 64 = 0.64 g. Answer: 0.64 g. Why not the others: 1.28 g: That uses one electron per copper ion instead of two. 0.32 g: That halves the correct mass. 64 g: That is the mass of one whole mole.
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