Question

Electrolysis of an aqueous solution of $AgN{O}_3$ with silver electrodes produces (i) at cathode while (ii) ions are dissolved from anode. When $Pt$ electrodes are used (iii) is produced at anode and (iv) at cathode.

	(i)	(ii)	(iii)	(iv)
(a)	$H_2$	$N{O}_3^{-}$	$O{H}^{-}$	$H_2$
(b)	$Ag$	$H^{+}$	$O_2$	$H_2$
(c)	$Ag$	$A{g}^{+}$	$O_2$	$Ag$
(d)	$Ag$	$H^{+}$	$A{g}^{+}$	$O_2$

• A. a
• B. b
• C. c
• D. d

Answer 1

Answer: (C)

When the electrode of the same material is used for example Ag. The metal itself gets oxidized and reduced on an electrode.
Cathode - Reduction $A{g}^{+}+e^{-}⟶Ag$
Anode - Oxidation $Ag⟶A{g}^{+}+e^{-}$
When platinum electrodes are used, $A{g}^{+}$from solution is reduced and deposited at cathode whereas $O_2$ is produced at the anode.
Cathode - Reduction $A{g}^{+}+e^{-}⟶Ag$
Anode - Oxidation $2H_{2}O⟶4H^{+}+O_2+4e^{-}$