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NEET levelSingle correct optionDifficulty 1 of 3ec160

In a hydrogen-oxygen fuel cell with concentrated aqueous $KOH$ as electrolyte, the reaction at the cathode is

A $H X_{2} + 2 OH X^{-} 2 H X_{2} O + 2 e X^{-}$
B $O X_{2} + 2 H X_{2} O + 4 e X^{-} 4 OH X^{-}$
C $2 H X^{+} + 2 e X^{-} H X_{2}$
D $O X_{2} + 4 H X^{+} + 4 e X^{-} 2 H X_{2} O$

Answer: B

At the cathode oxygen is reduced. In alkaline medium the reduction product is hydroxide:

O X_{2} + 2 H X_{2} O + 4 e X^{-} 4 OH X^{-}

. Option (A) is the anode reaction, (D) is oxygen reduction in acidic medium, and (C) is a reduction of

H X^{+}

that does not occur in this cell.

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