Question

Silver tarnishes due to the formation of silver sulfide (Ag₂S). Silver polish contains aluminum metal powder in an aqueous alkaline suspension. Write the balanced net ionic reaction equation to show how silver polish works to produce silver metal and solid aluminum hydroxide, Al(OH)₃. Specify the states of matter in your equation.

Answer 1

At anode Aluminium undergo oxidation to form Al³⁺ ions and produces electrons

At anode: Al_(s) -------> Al³⁺_(aq) + 3e-_(aq)    (Oxidation)

At cathode Silver sulfide undergo reduction to Silver metal

Ag₂S ------> 2Ag⁺ + S^2-

At cathode: 3Ag⁺_(aq) + 3e-_(aq) ------> Ag_(s)   (Reduction)

2Al³⁺_(aq) + 3S^2-_(aq) ------> Al_²S_3(aq)

The net reaction is

3 Ag₂S_(aq) + 2Al_(s) -------> 6Ag_(s) + Al₂S_3(aq)

Al₂S_3(aq) + 6H₂O_(aq) -------> 2Al(OH)_3(aq)+ 3H₂S_(aq)