Tarnished silver contains Ag2S. Can this tarnish be removed by placing the tarnished ware in an aluminium pan containing an inert electrolyte solution such as NaCl ? Given that the standard reduction potentials for the half reactions are :
`Ag2S(s)+2e^(-)to2Ag(s),+S^(2)(aq), E^(@)=-0.71" V"`.
`Al^(3+)(aq)+3e^(-) to Al(s), E^(@)=-1.66" V"`.

Explanation

Tarnish due to silver sulphide can be removed if the following cell reactions occurs :
`Ag_2 S + Al to Al^(3+) + 2 Ag + S^(2-)`
E.M.F. of the cell will be
`E^(Theta) = E^(Theta) (Ag_(2) S| 2Ag , S^(2-)) - E^(Theta) (Al^(3+)|Al)`
`= -0.71 - (-1.66) = + 0.95 V`
Since `E_(cell)^(@)` is positive , the reaction will occur and tarnish will be removed .