Arrange `K^(+) , Zn^(2+) , H^(+) and Cu^(2+)` ions in order of their tendency to be liberated at the cathode.
[Given:`mE_(Cu^(2+)|Cu)^(0) = +0.34 V , E_(2H^(+)|H_2)^(0) = 0.00 V, E_(Zn^(2+)|Zn = -.0.76 V, E_(K^(+)|K) = -2.93 V`]

Explanation

The increasing order of standard electrode potential of the given ions: `K_(K^(+)|K)^(0) lt E_(Zn^(2+)|Zn)^(0) lt E_(2H^(+)|H_(2))^(0) lt E_(Cu^(2+)|Cu)^(0)` . Among the given electrodes . `K^(+)|K` and `Cu^(2+)|Cu` have the lowest and highest reduction potential respectively. Thus , `Cu^(2+)` has the highest tendency to get reduced whereas K has the highest tendency to get oxidised. Thus the order of increasing tendencies to get liberated at cathode is :
`K^(+) lt Zn^(2+) lt H^(+) lt Cu^(2+)`