First slide

Batteries

Question

Which of the following statement is incorrect for dry cell ?

Easy

A

Reaction at cathode ${MnO}_{2} + {NH}_{4}^{+} + e^{-} ⟶ MnO (OH) + {NH}_{3}$
B

Manganese is reduced from +5 to +4 state
C

Cell potential is 1.5 V
D

Ammonia form complex with Zn²⁺ to give ${[Zn {({NH}_{3})}_{4}]}^{2 +}$

Solution

$Anode Zn (s) ⟶ {Zn}^{2 +} (aq) + 2 e^{-}$
$Cathode {MnO}_{2} + {NH}_{4}^{+} + e^{-} ⟶ MnO (OH) + {NH}_{3}$
At cathode manganese is reduced from +4 oxidation state to +3 oxidation state. Ammonia produced in reaction from complex with Zn²⁺ to give ${[Zn {({NH}_{2})}_{4}]}^{2 +}$ . The cell has potential of 1.5 V.

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