Question

When electrolysis of $CuS{O}_4$(aq) by using copper electrodes is performed then the concentration of $C{u}^{2+}$ will.

• A. increase
• B. decrease
• C. remain constant

Answer 1

The correct option is C remain constant

Anode and cathode are copper rods, both dipped in the same electrolytic solution.
At anode
$C{u}^{2+}⟶Cu+2e^{-}$
$E^0=0.34V$
$S{O}_4^{2-}⟶S_2{O}_8^{2-}+2e^{-}$
$E^0=-2.5$
$H_{2}O⟶O_2+4O{H}^{-}+4e^{-}$
$E^0=-1.23V$
Oxidation of Cu happens at the anode.

Possible reactions at the cathode:
$C{u}^{2+}+2e^{-}⟶Cu$
$E^0=-0.34V$
$H_{2}O+2e^{-}⟶H_2+2H^{+}$
$E^0=-0.83$
Reaction at cathode $C{u}^{2+}+2e^{-}⟶Cu$
Copper ions are getting reduced and copper is getting oxidised again producing copper ions that go back into the solution. So, the concentration remains constant in solution.