NCERT Class XII Chemistry
Chapter - Electrochemistry
Questions with Solutions
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Question : 12
Total: 32
How much charge is required for the following reductions:
(i) 1 mol ofA l 3 + A l
(ii) 1 mol ofC u 2 + C u
(iii) 1 mol ofM n O 4 – M n 2 +
(i) 1 mol of
(ii) 1 mol of
(iii) 1 mol of
Solution:
(i) The given reaction is
+
→ A l
∴ 3 mole electrons are needed for reduction of 1 mole ofA l 3 + A l
3 mole electrons = 3 Faraday
= 3 × 96500 coulombs
= 2.895 × 105
(ii) The given reaction is
+
→ C u
∴ 2 mole electrons are needed for reduction of 1 mole ofC u 2 + C u
2 mole electrons = 2 Faraday
= 2 × 96500 coulombs
= 1.93 × 105
(iii)The given reaction is
+ 8 H + +
→ M n 2 + ( a q ) + 4 H 2 O ( l ) M n O 4 – M n 2 + .
5 mole electrons = 5 Faradays
= 5 × 96500 coulombs
= 4.825 × 105
∴ 3 mole electrons are needed for reduction of 1 mole of
3 mole electrons = 3 Faraday
= 3 × 96500 coulombs
= 2.895 × 10
(ii) The given reaction is
∴ 2 mole electrons are needed for reduction of 1 mole of
2 mole electrons = 2 Faraday
= 2 × 96500 coulombs
= 1.93 × 10
(iii)The given reaction is
5 mole electrons = 5 Faradays
= 5 × 96500 coulombs
= 4.825 × 10
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