In fuel cell H 2 and O 2 react to produce electricity. In the process, H 2 gas is oxidised at the anode and O 2 at cathode. If 44 . 8 litre of H 2 at 25 ° C and 1 atm pressure reacts for 10 minutes, what is average current produced? If the entire current is used for electro deposition of Cu from Cu 2 + , how many grams of Cu is deposited?

According to question, Oxidation at anode: 2 H 2 ( g ) + 4 OH - ( aq ) → 4 H 2 O ( l ) + 4 e - 1 mole of hydrogen gas produces 2 moles of electrons at 25 ° C and 1 atm pressure, 1 mole of hydrogen gas occupies = 22 . 4 litres The number of moles of hydrogen gas produced = 1 mole 22 . 4 litres x 44 . 8 litres Therefore, 2 of moles of hydrogen produces 4 moles of electrons i.e., 4 F charge. We know that Q = It I = Q t = 4 F 10 mins = 4 x 96500 C 10 x 60 s I = 643 . 33 A Electro deposition of copper Cu 2 + ( aq ) + 2 e - → Cu ( s ) 2 moles of electrons ( 2 F ) deposit 1 mole of copper i.e. 63 . 5 g . If the entire current produced in the fuel cell i.e., 4 F is utilised for electrolysis, then 2 × 63 . 5 i.e., 127 . 0 g copper will be deposited at cathode.

The same amount of electricity was passed through two separate electrolytic cells containing solutions of nickel nitrate and chromium nitrate respectively. If 2 . 935 g of Ni was deposited in the first cell. The amount of Cr deposited in the another cell? Given: molar mass of Nickel and chromium are 58 . 74 and 52 g mol - 1 respectively.

According to Faraday’s second Law, when same quantity of charge is passed through the solutions of different electrolytes, the amount of substances liberated at the respective electrodes are directly proportional to their electrochemical equivalents. Ni 2 + ( aq ) + 2 e - → Ni ( s ) Cr 3 + ( aq ) + 3 e - → Cr ( s ) According to Faraday’s second Law, m Ni Z Ni = m Cr Z Cr . . . . . . . . ( 1 ) Here, m is the mass deposited and Z is the electrochemical equivalent. Also, Z = Molar mass n × 96500 . . . . . . . . . ( 2 ) Given that 2 . 935 g of Nickel is deposited and the molar masses of Nickel and chromium are 58 . 74 and 52 g mol - 1 respectively. Let the amount of Cr deposited be x g . Hence, from ( 1 ) and ( 2 ) 2 . 935 × 2 × 96500 58 . 74 = x × 3 × 96500 52 On solving, x = 1 . 732 g Therefore, the amount of Cr deposited in the another cell is 1 . 732 g .

The conductivity of 0 . 20 M solution of KCl at 298 K is 0 . 0248 S cm - 1 . Calculate its molar conductivity.

Molarity of solution, M = 0 . 20 Conductivity, k = 0 . 0248 S cm - 1 = 2 . 48 × 10 - 2 ohm - 1 cm - 1 Molar conductivity, ∧ m = k × 1000 M ohm - 1 cm 2 mol - 1 = 2 . 48 × 10 - 2 × 1000 0 . 20 ohm - 1 cm 2 mol - 1 = 124 . 0 S cm 2 mol - 1

HARD

12th Tamil Nadu Board

IMPORTANT

Earn 100

Calculate the potential of hydrogen electrode in contact with a solution whose $pH$ is 10.

Important Questions on Electro Chemistry

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 31

Following cell reaction occurs in cell:

2 {Fe}^{+ 3} (aq) + 2 I^{-} (aq) \to 2 {Fe}^{+ 2} (aq) + I_{2} (s)

. At

298 K

the standard cell potential of this cell

{E^{o}}_{cell} = 0.236 V

. Calculate standard Gibb's free energy and the equilibrium constant of the cell reaction.

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 32

In fuel cell

H_{2}

and

O_{2}

react to produce electricity. In the process,

H_{2}

gas is oxidised at the anode and

O_{2}

at cathode. If

44.8

litre of

H_{2}

25 ° C

and

1 atm

pressure reacts for

10

minutes, what is average current produced? If the entire current is used for electro deposition of

Cu

from

{Cu}^{2 +}

, how many grams of

Cu

is deposited?

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 33

The same amount of electricity was passed through two separate electrolytic cells containing solutions of nickel nitrate and chromium nitrate respectively. If

2.935 g

Ni

was deposited in the first cell. The amount of

Cr

deposited in the another cell? Given: molar mass of Nickel and chromium are

58.74

and

52 g {mol}^{- 1}

respectively.

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 34

Describe the construction and working of Daniell cell.

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 35

Explain the working of salt bridge.

MEDIUM

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 36

The conductivity of

0.20 M

solution of

KCl

298 K

0.0248 S {cm}^{- 1}

. Calculate its molar conductivity.

EASY

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 37

Write any two differences between electrolytic and metallic conductors?

MEDIUM

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 9 - Electro Chemistry>Exercise>Q 38

The resistance of a

0.15 N

solution of an electrolyte is

50 Ω

. The specific conductance of a solution is

2.4 {Sm}^{- 1}

. The resistance of

0.5 N

solution of same electrolyte measured using the same conductivity cell is

480 Ω

. Find the equivalent conductivity of

0.5 N

solution of the electrolyte.

Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.

Important Questions on Electro Chemistry

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Calculate the potential of hydrogen electrode in contact with a solution whose $pH$ is 10.