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During the discharge of a lead storage battery, the density of sulphuric acid fell from $1.294$ to $1.139 g$ ${mL}^{- 1} \cdot H_{2} {SO}_{4}$ of density $1.294 {gmL}^{- 1}$ is $39 %$ and that of density $1.139 g \cdot {mL}^{- 1}$ is $20 %$ by weight. The battery holds $3.5 L$ of acid and the volume practically remains constant during discharge. Calculate the number of ampere hours for which the battery must have been used. The discharging and charging reactions are.

$Pb + {SO}_{4}^{2 -} \to {PbSO}_{4} + 2 e^{-}$ (Charging)
${PbO}_{2} + 4 H^{+} + {SO}_{4}^{2 -} + 2 e^{-} \to {PbSO}_{4} + 2 H_{2} O$ (discharging)

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Important Questions on Electrochemistry

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IMPORTANT

Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 26

EMF of the cell

Zn |{ZnSO}_{4} (a = 0.2)| |{ZnSO}_{4} (a_{2})| Zn

- 0.0088 V

25 ° C .

Calculate the value of

a_{2} .

If your answer is

10^{- x}

then

x

is :

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Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 27

The standard reduction potential values,

E ° ({Bi}^{3 +} / Bi)

and

E ° ({Cu}^{2 +} / Cu)

are

0.226 V

and

0.344 V

respectively. A mixture of salts of bismuth and copper at unit concentration each is electrolysed at

25 ° C

. To what value can

[{Cu}^{2 +}] [{Cu}^{2 +}]

be brought down before bismuth starts to deposit, in electrolysis.

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Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 28

A big irregular shaped vessel contained water, the sp. conductance of which was

2.56 \times 10^{- 5} {mhocm}^{- 1}

500 g

NaCl

was then added to the water and the specific conductance after the addition of

NaCl

, was found to be

3.10 \times 10^{- 5} {mhocm}^{- 1}

. Find the capacity of the vessel if it is fulfilled with water. (

λ NaCl = 149.9

). If your answer is

x \times 10^{8} cc

then

x

is:

MEDIUM

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Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 29

The equivalent conductance of

0.10 N

solution of

{MgCl}_{2}

97.1 {mhocm}^{2}

{eq}^{- 1}

. A cell with electrodes that are

1.50 {cm}^{2}

in surface are and

0.50 cm

apart is filled with

0.1 {NMgCl}_{2}

solution. How much current will flow when the potential difference between the electrodes is

5

volts? If your answer is

x \times 10^{- 1}

then

x

is:

EASY

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Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 30

Calculate

K_{a}

of acetic acid if its

0.05 N

solution has equivalent conductance of

7.36 m ho {cm}^{2}

25 ° C

(λ_{{CH}_{3} COOH}^{\infty} = 390.70)

If your answer is

x \times 10^{- 5}

then

x

is :

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Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 31

Cd

amalgam is prepared by electrolysis of a solution

{CdCl}_{2}

using a mercury cathode. What time (in sec.) current of

5

A should be passed in order to prepare

12 % Cd - Hg

amalgam on a cathode of

2 g, Hg

(atomic weight of

Cd = 112.4

)

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Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 32

After electrolysis of

NaCl

solution with inert electrodes for a certain period of time,

600 mL

of the solution was left. Which was found to be

1 N

NaOH

. During the same time,

31.75 g

Cu

deposited in the copper voltameter in series with the electrolytic cell. Calculate the percentage yield of

NaOH

obtained.

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Beta Question Bank for Engineering: Chemistry>Chapter 9 - Electrochemistry>EXERCISE-3>Q 33

The e.m.f. of the cell obtained by combining

Zn

and

Cu

electrode of a Daniel cell with

N

calomel electrode in two different arrangements are

1.083 V

and

0.018 V

respectively at

25 ° C

. If the standard reduction potential of

N

calomel electrode is

0.28 V

find the emf of Daniel cell.

Important Questions on Electrochemistry

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