(a) What are fuel cells ? Explain the electrode reactions involved in the working of `H_(2)-O_(2)` fuel cell.
(b) Represent the galvanic cell in which the reaction
`Zn(s) + Cu^(2)(aq) to Zn^(2+) (aq) + Cu(s)` takes place.

Explanation

Those galvanic cells which give us direct electrical energy by the combustion of fuels like hydrogen, methane, methanol etc. are called fuel cell.
The reactions taking place in hydrogen – oxygen fuel cell:

At cathode : `O_(2(g) + 2H_(2)O _(1) + 4e^(-)to 4OH_(aq)^(-)`
`underline(At anode : 2H_(2(g)+ 4OH^_(aq)^(-)rightarrow
4H_(2)O_((1))+ 4e`
Net reaction : `2H_(2)(g) + O_(2)(g) rightarrow 2H_(2) O _(1)`