Electrochemistry Ques 20
20. On electrolysis of dilute sulphuric acid using platinum electrodes, the product obtained at the anode will be
[1992]
(a) hydrogen
(b) oxygen
(c) hydrogen sulphide
(d) sulphur dioxide.
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Answer:
Correct Answer: 20.(b)
Solution:
(b) During electrolysis of sulphuric acid, the following processes are possible at cathode:
$2 H_2 O(l) \longrightarrow O_2(g)+4 H^{+}(aq)+4 e^{-}$,
$\hspace{30mm} E^{\circ}=+1.23 V$
$2 SO_4^{2-}(aq) \longrightarrow S_2 O_8^{2-}(aq)+2 e^{-}, E^{\circ}=+1.96 V$
For dilute sulphuric acid, first reaction is preferred but for concentrated acid, second reaction is preferred.
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