Question on: JAMB Chemistry - 2024

Calculate the mass of Magnesium that will be liberated from its salt by the same quantity of electricity that liberated 16.0 g of Silver.

[Mg = 24.0, Ag = 108 ]

3.65 g

3.56 g

1.87 g

1.78 g

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Correct Option: D

Here's how to solve this problem using Faraday's laws of electrolysis:

1. Write the half-reactions:

Ag⁺ + e⁻ → Ag
Mg²⁺ + 2e⁻ → Mg

2. Determine the number of moles of silver liberated:
Moles of Ag = 16.0 g / 108 g/mol ≈ 0.148 mol

3. Determine the number of moles of electrons involved:
1 mole of Ag requires 1 mole of electrons → 0.148 mol of electrons

4. Determine the mass of magnesium liberated:
1 mole of Mg requires 2 moles of electrons → 0.148 / 2 = 0.074 mol of Mg
Mass of Mg = 0.074 × 24 g/mol ≈ 1.78 g