Paper 3 · electrochemistry

A research student performed a constant current electrolysis of silver solution using a carbon electrode as the cathode. The electrolysis was allowed to proceed for 0.25 hours at a limiting current of 1.25 A. What is the mass of silver deposited?

A33.75 g

B1.26 g

C0.63 g

D0.02 g

Explanation: The marking scheme gives answer B. Charge = I × t = 1.25 × (0.25 × 3600) = 1125 C. Moles of electrons = 1125/96500 = 0.01166 mol. Moles of Ag = 0.01166 mol. Mass = 0.01166 × 108 = 1.26 g.

ZIMSEC Chemistry Paper 3, June 2009, Q8

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A research student performed a constant current electrolysis of silver solution using a carbon electrode as the cathode. The electrolysis was allowed to proceed for 0.25 hours at a limiting current of 1.25 A. What is the mass of silver deposited?

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