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Secondary Cells

Which of the ...

Question

Which of the following reactions occurs at cathode during charging of storage battery?

A

P b^{2 +} + 2 e^{-} \to P b

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B

P b \to P b^{2 +} + 2 e^{-}

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C

P b^{2 +} + S O_{4}^{2 -} \to P b S O_{4}

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D

P b S O_{4} + 2 H_{2} O \to P b O_{2} + 4 H^{+} + S O_{2}^{2 -} + 2 e^{-}

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Solution

The correct option is A $P b^{2 +} + 2 e^{-} \to P b$
(i) Cell reaction during discharge at anode:-
$\to$ Oxidation reaction at anode[negative electrode]:-
$P b_{(s)} \to P b_{(a q)}^{2 +} + 2 e^{-}$ ---------[oxidation reaction].
$P b_{(a q)}^{2 +} + S O_{4 (a q)}^{2 -} \to P b S O_{4 (s)}$ .
Final Reaction:- $P b_{(s)} + S O_{4 (a q)}^{2 -} \to P b S O_{4 (s)} + 2 e^{-}$ [overall oxidation at anode].

(ii) Cell reaction during recharge:-
The reverse of oxidation at anode during discharge is the reduction reaction at cathode during recharging.
$P b_{(a q)}^{2 +} + 2 e^{-} \to P b_{(s)}$ ---------[reduction].
$P b S O_{4 (s)} \to P b_{(a q)}^{2 +} + S O_{4 (a q)}^{2 -}$
Final Reaction:- $P b S O_{4 (s)} + 2 e^{-} \to P b_{(s)} + S O_{4 (a q)}^{2 -}$

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Similar questions

Q. During the discharge of a lead storage battery, density of

H_{2} S O_{4}

1.294

1.139

. S u l p h u r i c a c i d o f d e n s i t y

i s

b y w e i g h t a n d t h a t o f d e n s i t y

i s

b y w e i g h t . T h e b a t t e r y h o l d

o f t h e a c i d a n d v o l u m e r e m a i n s p r a c t i c a l l y c o n s t a n t d u r i n g d i s c h a r g e . C a l c u l a t e a m p e r e - h o u r o f w h i c h t h e b a t t e r y m u s t h a v e b e e n u s e d . T h e c h a r g i n g a n d d i s c h a r g i n g r e a c t i o n s a r e :

Pb + SO_{4}^{2-} \rightarrow PbSO_{4} + 2e^{-}

(c h a r g i n g)

PbO_{2} + 4H^{+} + SO_{4}^{2-} + 2e^{-}\rightarrow PbSO_{4} + 2H_{2}O$ (discharging).

Q. The electrode reactions for charging of a lead battery are:

P b S O_{4} + 2 e \to P b + S O_{4}^{2 -}

P b S O_{4} + 2 H_{2} O \to P b O_{2} + S O_{4}^{2 -} + 4 H + 2 e

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H_{2} 3 O_{4}

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Q. During the discharge of a lead storage battery, the density of sulphuric acid fell from 1.294 to 1.139

g m L^{- 1}

H_{2} S O_{4}

1.294 g m L^{- 1}

is 39% and that of density

1.139 g m L^{- 1}

is 20% by weight.The battery holds 3.5 L of acid and the volume practically remains constant during discharge. The number of ampere hours for which the battery must have been used are........................
The discharging and charging reactions are:

P b + S O_{4}^{2 -} \to P b S O_{4} + 2 e^{-}

P b O_{2} + 4 H^{+} + S O_{4}^{2 -} + 2 e^{-} \to P b S O_{4} + 2 H_{2} O

Q. During the discharge of a lead storage battery, the density of sulphuric acid fell from

1.294

1.139 g m l^{- 1}

. Sulphuric acid of density

1.294 g m l^{- 1}

is 39% by weight and that of density

1.139 g m l^{- 1}

is 20% by weight. The battery holds 3.5 L of the acid and the volume remained practically constant during the discharge. Find the number of ampere-hours for which the battery must has been used.

The charging and discharging reactions are as follows:

$P b + S O_{4}^{2 -} \to P b S O_{4} + 2 e^{-}$ (charging)

$P b O_{2} + 4 H^{\oplus} + S O_{4}^{2 -} + 2 e^{-} \to P b S O_{4} + 2 H_{2} O$ (discharging)

During the discharge of a lead storage battery, the density of sulphuric acid fell from $1.294$ to $1.139$ gm $L^{- 1}$ . Sulphuric acid of density $1.294$ gm $L^{- 1}$ is $39$ % by weight and that of density 1.139 gm $L^{- 1}$ is $20$ % by weight. The battery holds $3.5$ litres of acid and the column practically remained constant during the discharge.

Calculate the number of ampere-hours for which the battery must have been used. The charging and discharging reactions are :

$P b + S O {_{4}}^{2 -} \to P b S O_{4} + 2 e^{-}$ (charging)

$P b O_{2} + 4 H^{+} + S O {_{4}}^{2 -} + 2 e^{-} \to P b S O_{4} + 2 H_{2} O$ (discharging)

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