Question

(b) Tarnished silver contains Ag\(_2\)S. Can this tarnish be removed by placing tarnished silverware in an aluminium pan containing an inert electrolytic solution such as NaCl? The standard electrode potential for half-reactions:
\[ \text{Ag}_2\text{S}(s) + 2e^- \rightarrow 2\text{Ag}(s) + \text{S}^{2-} \, \, E^\circ = -0.71 \, V \] \[ \text{Al}^{3+} + 3e^- \rightarrow 2\text{Al}(s) \, \, E^\circ = -1.66 \, V \]

Hint:

A more negative electrode potential means a stronger reducing agent, which is why aluminium can reduce silver tarnish.

Answer 1

Yes, tarnish can be removed by placing tarnished silverware in an aluminium pan containing NaCl solution. The oxidation of aluminium at the anode releases electrons, which are used to reduce silver ions (Ag\(_2\)S) at the cathode. Since aluminium has a more negative standard electrode potential (\(-1.66\,V\)) compared to silver tarnish (\(-0.71\,V\)), aluminium will undergo oxidation and the silver tarnish will be reduced back to metallic silver.