Question 9

The simplified diagram below represents an electrochemical cell used for the purification of copper.

9.1 Define the term electrolysis. (2)

9.2 Give a reason why a direct-current (DC) source is used in this experiment. (1)

9.3 Write down the half-reaction which takes place at electrode A. (2)

9.4 Due to small amounts of zinc impurities in the impure copper, the electrolyte becomes contaminated with Zn2+ ions.

Refer to the attached Table of Standard Reduction Potentials to explain why the Zn2+ ions will not influence the purity of the copper obtained during this process. (3)

9.5 After the purification of the impure copper was completed, it was found that 2,85 x 10-2 moles of copper were formed.

The initial mass of electrode B was 2,0 g. Calculate the percentage of copper that was initially present in electrode B. (4)


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