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Electrochemistry

Short Answer Type

131. Write the cell reactions which occur in lead storage battery (i) when the battery is in use and (ii) when the battery is on charging.

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132. The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 s cm^–1. Calculate its molar conductivity.

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133.

How much charge is required for the following reductions:
1 mol of Al³⁺ to Al?

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134.

How much charge is required for the following reductions:
1 mol of Cu²⁺ to Cu?

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135.

How much charge is required for the following reductions:
1 mol of MnO₄^– to Mn²⁺?

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136. How much electricity in terms of Faraday is required to produce
20.0 g of Ca from molten CaCl₂?

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137. How much electricity in terms of Faraday is required to produce
40.0 g of Al from molten Al₂O₃?

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138. How much electricity is required in coulomb for the oxidation of
1 mol of H₂O to O₂ ?

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139. How much electricity is required in coulomb for the oxidation of
1 mol of FeO to Fe₂O₃

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140. A solution of Ni(NO₃)₂ is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

Given that ,

Current, I = 5A

Time, t = 20 × 60 = 1200 s (1 min = 60 second)

Charge = I × t

= 5 × 1200

= 6000 Coulombs

Charge on Ni

No₃ has –1 charge always so that

Ni +2(NO₃) =0

Ni + 2(–1) = 0

Ni = +2

Charge required to deposited 1 mol of Ni = nF

= 2 × 96487 Coulombs

= 192974 Coulombs

1 mol of Ni = 58.7 g (use periodic table to get this value)

192974 Coulombs will generate = 58.7 g of Ni

6000 Coulombs will generate = 58.7 g × 6000 Coulombs /192974 Coulombs

= 1.825 g

Hence, 1.825 g of nickel will be deposited at the cathode.

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Previous Year Papers

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Test Yourself

Short Answer Type

140. A solution of Ni(NO3)2 is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

140. A solution of Ni(NO₃)₂ is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?