Give reason
(a) Why does an alkaline medium inhibit the rusting of iron ?
(b) Why does a dry cell become dead after a long time even if it has not been used ?
(c) Why is zinc better than tin in protecting iron from corrosion ?

Explanation

(a) Rusting of iron takes place in the presence of `H^+`. Alkaline medium neutralises `H^+` ions and inhibits the process of rusting.
(b) A dry cell becomes dead after a long time even if it has not been used. This is because acidic `NH^4Cl` which is a salt of weak base and strong acid, corrodes zinc container.
(c) Zinc protects iron from corrosion because reduction potential of `Zn^(2+)` is lower than that of `Fe^(2+)`, but that of `Sn^(2+)` is higher than that of `Fe^(2+)` .