3) Tarnished silver contains Ag2S. The tarnish can be removed by placing silverware in an aluminum pan containing an inert electrolyte Such as NaCl. Explain the electrochemical principle for this procedure. The standard reduction potential for the half-cell reaction: Ag2S (s) + 2e-  2Ag (s) + S-2 (aq) is -0.71 V

Tarnished silver ware is cleaned by placing it in an aluminium pan as E°cell is positive.

Explanation:

The tarnish silver due to silver sulphate is removed by placing the tarnished ware in an aluminium pan. Certainly, aluminium is a stronger reducing agent than silver. Hence, it reduces the silver ions(Ag+) to metallic silver. The silvery white white colour will slowly get deposited on the walls of silwer ware and then the tarnish will be removed.

Al(s)+ 3Ag+ (aq)→ Al3+ (aq)+ 3Ag(s)

E° cell = E ° cathode - E° anode

 = (-0.71)- (-1.66) = 0.95 V is positive.

Hence, the reaction is feasible and the tarnish will be removed.

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