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Standard XII

Chemistry

Secondary Cells

While chargin...

Question

While charging the lead storage battery, ______________ .

P b {S O}_{4}

on anode is reduced to

P b

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P b {S O}_{4}

on cathode is reduced to

P b

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P b {S O}_{4}

on cathode is oxidised to

P b

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P b {S O}_{4}

on anode is oxidised to

P b O_{2}

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Solution

The correct options are
C $P b {S O}_{4}$ on anode is oxidised to $P b O_{2}$
D $P b {S O}_{4}$ on cathode is reduced to $P b$
During charging, $P b O_{2}$ is formed at the anode from $P b S O_{4}$ (oxidation of $P b$ ion) and $P b$ is formed at cathode from $P b S O_{4}$ (reduction of $P b$ ion).
Hence options (B) and (D) are correct.

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Similar questions

Q. In a lead storage battery, the anode reaction is,

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

Weight in g of Pb would be used up for battery to use for 1 ampere hour is___________. (write the nearest integer value)

Q. Which substance/ion is oxidised and which substance/ion is reduced in the following reactions?

P b S + 4 H_{2} O_{2} \to P b S O_{4} + 4 H_{2} O

Electrochemical Battery

An electrochemical battery is a device powered by oxidation and reduction reactions that are physically separated. So that the electrons must travel through a wire from the reducing agent to the oxidizing agent.

The reducing agent loses electrons and is oxidized in a reaction that takes place at an electrode is called the anode. The oxidizing agent gains electrons and is reduced in a reaction that takes at an electrode is called the cathode.

To maintain a net zero charge in each compartment, there is a limited flow of ions through a salt bridge.

For example, in a car battery the reducing agent is oxidized by the following reaction, which involves a lead (

P b

) anode and sulfuric acid (

H_{2} S O_{4}

). Lead sulfate (

P b S O_{4}

), protons (

H

), and electrons (

e^{-}

) are produced.

At the cathode, the below reaction occurs :

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

PbSO_4+2H_2O$

At the anode, the below reaction occurs :

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

Electrons are produced by a chemical reaction that takes place at the:

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

H_{2} S O_{4}

fell from

1.294

1.139

\ g/mL

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

1.294

i s

H_{2}SO_{4}

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

1.139\ g/mL

i s

H_{2}SO_{4}

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

3.5\ litre

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

The electrolyte in the battery is an aqueous solution of

H_{2} 3 O_{4}

. After this battery has been charged:

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While charging the lead storage battery, ______________ .

The correct options are C PbSO4 on anode is oxidised to PbO2 D PbSO4 on cathode is reduced to PbDuring charging, PbO2 is formed at the anode from PbSO4 (oxidation of Pb ion) and Pb is formed at cathode from PbSO4 (reduction of Pb ion).Hence options (B) and (D) are correct.