Question

Electrolysis of an aqueous solution of $AgNO_3$ 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)$\,\,$	$H_2\,\,$	$NO^{-}_{3}\,$	$OH^-\,\,$	$H_2\,\,$
(b)$\,\,$	$Ag\,\,$	$H^+\,\,$	$O_2\,\,$	$H_2\,\,$
(c)$\,\,$	$Ag\,\,$	$Ag^+\,\,$	$O_2\,\,$	$Ag\,\,$
(d)$\,\,$	$Ag\,\,$	$H^+\,\,$	$Ag^+\,\,$	$O_2$

• 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 $Ag ^{+}+ e ^{-} \longrightarrow Ag$
Anode - Oxidation $Ag \longrightarrow Ag ^{+}+ e ^{-}$
When platinum electrodes are used, $Ag ^{+}$from solution is reduced and deposited at cathode whereas $O _{2}$ is produced at the anode.
Cathode - Reduction $Ag ^{+}+ e ^{-} \longrightarrow Ag$
Anode - Oxidation $2 H _{2} O \longrightarrow 4 H ^{+}+ O _{2}+4 e ^{-}$