Question

A solution containing one mole per litre each of $Cu(N{O}_3{)}_2,AgN{O}_3,H{g}_2(N{O}_3{)}_2$ and $Mg(N{O}_3{)}_2$ is being electrolysed by using inert electrodes. The values of standard electrode potentials in volt (reduction potentials) are:

$Ag/A{g}^{+}=0.80,$ $2Hg/H{g}_2^{2+}=0.79$
$Cu/C{u}^{2+}=+0.34$ and $Mg/M{g}^{2+}=-2.37$

With increasing voltage, the sequence of deposition of metals on the cathode will be?

• A. $\text{Ag, Hg, Cu, Mg}$
• B. $\text{Mg, Cu, Hg, Ag}$
• C. $\text{Ag, Hg, Cu}$
• D. $\text{Cu, Hg, Ag}$

Answer 1

The correct option is C $\text{Ag, Hg, Cu}$

Higher the reduction potential, higher is the tendency to deposition.

Reduction potential order is Ag > Hg > Cu so they deposit according to that order but as reduction potential of Mg is negative so it doesnt have any tendency to deposit and it can not be obtained by electrolysing the aqueous salt solutions.

Hence,option C is correct.