KVPY Sample Paper KVPY Stream-SX Model Paper-11

Electrolysis of a solution of \[HSO_{4}^{\,-}\] ions produces \[{{S}_{2}}{{O}_{8}}^{-\,-}.\] Assuming 75% current efficiency, what current should be employed to achieve a production rate of 1 mole of \[{{S}_{2}}{{O}_{8}}^{-\,-}\] per hour?

A) +71.5 amp

B) 35.7 amp

C) 142.96 amp

D) 285.93 amp

Correct Answer: A

Solution :

\[2HSO_{4}^{-}\xrightarrow{{}}{{S}_{2}}O_{8}^{-\,-}+2{{H}^{+}}+2{{e}^{-}}\]

so required rate\[~=1\,\,\text{mole}/hr\]\[=2\,\,\text{mole}\] of \[{{e}^{-}}/hr\]

\[=\frac{2\times 96500\,\,C}{3600\,\,\sec }=\frac{2\times 965}{36}A\simeq 53.6\,\,A\]

so required current \[=\frac{4}{3}\times 53.6\,A=71.4\,A\]