Question

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

Answer 1

Correct Answer - C
A cation havig highest reduction potential will be reduced first and so on. However, `Mg^(2+)` in aqueous
solution will not be reduced `(E_(Mg^(2+)//Mg)^(o)ltE_(H_(2)O//(1)/(2)H_(2)+OH^(-)))`
Instead water would be reduced in preference.