A solution containing one mole per litre of each `Cu(NO_(3))_(2), AgNO_(3), Hg_(2)(NO_(3))_(2)` is being electrolysed by using inert electrodes. The values of standard electrode potentials in volts (reduction potentials) are
`Ag^(+)//Ag = +0.80 V, HG_(2)^(2+)//Hg = +0.79 V`
`Cu^(+)//Cu = +0.34 V, Mg^(2+)//Mg = -2.37 V`
With increasing valtage, the sequence of deposition of metals on the cathode will be

Options

A. Ag,Hg,Cu,Mg
B. Mg,Cu,Hg,Ag
C. Ag,Hg,Cu
D. Cu,Hg,Ag

Answer

A

Explanation

The ions be arranged as under on the bases of their reduction potential values
`Ag^(+) gt Hg_(2)^(2+) gt Cu^(2+) gt Mg^(2+)`
`(+0.80 )" "(+0.79)" "(+0.34)" "(-2.37)`
`Mg^(2+)` will not be reduced as its reduction potenital value is much lower than that of water (-.834)
On the basis of above reduction potential value is much lower than that of water (-0.834).
On the basis of above reduction potential values we can easily conclude that the deposition of metals will be in the order Ag, Hg, Cu.