CBSE Class 12 · 2005 · Redox Reactions and ElectrochemistryShort Answer

Predict the products of electrolysis obtained at the electrodes in each case when the electrodes used are of platinum:
i) an aqueous solution of AgNO

_{3}

ii) an aqueous solution of H

_{2}

_{4}

Answer: (i) Cathode: Ag deposited; anode: O₂ evolved. (ii) Cathode: H₂; anode: O₂.

Solution

(i) AgNO

_{3}

(aq): at the cathode, Ag

^{+}

(higher reduction potential than water) is reduced — silver is deposited: Ag

^{+}

+ e

^{-} \to

Ag.
At the anode, water is oxidised — oxygen is evolved: 2H

_{2}

\to

_{2}

+ 4H

^{+}

+ 4e

^{-}

(NO

_{3}^{-}

is not oxidised).
(ii) H

_{2}

_{4}

(aq): at the cathode hydrogen is evolved (2H

^{+}

+ 2e

^{-} \to

_{2}

); at the anode water is oxidised to O

_{2}

(SO

_{4}^{2 -}

is not discharged).

CBSE Class 12 Board · 2005 · Subjective