What quantity of electricity will liberate 0.125 mole of oxygen…

What quantity of electricity will liberate 0.125 mole of oxygen molecules during the electrolysis of dilute sodium chloride solution?

A. 24,125 C

B. 48,250 C

C. 72,375 C

D. 96,500 C

QUICK ANSWER…

A

DETAILS…

According to Faraday’s law of electrolysis,

• For a mono-valent ion (eq: H⁺, Cl¯, Na⁺, K⁺, F¯), 1 mole of its atom or molecule will be liberated by 96,500 coulombs of electricity.
• For a di-valent ion (eq: Mg²⁺, O²¯, Ca²⁺), 1 mole of it will be liberated by 2 × 96500 = 193,000 coulombs of electricity.
• For a tri-valent ion (eq: Al³⁺), 1 mole of it will be liberated by 3 × 96500 = 289,500 coulombs of electricity.

To resolve this problem, oxygen is di-valent, it means:

1 mole of oxygen molecule = 193000C, therefore,

0.125 mole will be = X

Cross multiplying to find X, we have:

X(1) = 0.125 × 193000

X = 24,125 coulombs

Now for the right answer to the above question:

1. Option A is correct.
2. Option B is incorrect.
3. C is incorrect.
4. D is not the correct answer.

KEY-POINTS…

You may please note these/this:

• For a mono-valent ion, the quantity of electricity needed to liberate 1 mole of its product = 96500C
• For a di-valent ion, the quantity of electricity needed to liberate 1 mole of its product = 2 × 96500 = 193000C
• For a trivalent ion like aluminum ion, the quantity of electricity required to liberate 1 mole of its product will be = 3 × 96500C = 289500C
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/ culled from 2020 JAMB-UTME chemistry past question 27 /