Electrolysis (IGCSE)
Year 10 (IGCSE) ⚗️ Chemical Reactions Apply Q = It; predict products; solve quantitative electrolysis problems.
⚡ Quantitative Electrolysis
The amount deposited is proportional to charge passed.
Key Formulas
$$Q = I \times t \quad \text{(coulombs)} \qquad \text{mol e}^- = \frac{Q}{F} \quad (F = 96{,}500 \text{ C/mol})$$
$$\text{mol product} = \frac{\text{mol e}^-}{n} \quad (n = \text{electrons per ion})$$🔋 Electrode Products
| Electrolyte | Cathode product | Anode product |
|---|---|---|
| Dilute H₂SO₄ | H₂ | O₂ |
| CuSO₄ (inert electrodes) | Cu | O₂ |
| CuSO₄ (Cu electrodes) | Cu deposited | Cu dissolves |
| NaCl(aq) | H₂ | Cl₂ |
🧮 Worked Example
2 A for 1 hour through CuSO₄. Mass of Cu deposited?
Q = 2 × 3600 = 7200 C
mol e⁻ = 7200/96500 = 0.0746 mol
Cu²⁺ + 2e⁻ → Cu, so mol Cu = 0.0746/2 = 0.0373 mol
Mass = 0.0373 × 63.5 = 2.37 g
Q = 2 × 3600 = 7200 C
mol e⁻ = 7200/96500 = 0.0746 mol
Cu²⁺ + 2e⁻ → Cu, so mol Cu = 0.0746/2 = 0.0373 mol
Mass = 0.0373 × 63.5 = 2.37 g
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Interactive Demonstration — Electrolysis (IGCSE)
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⚡ Electrolysis Calculator (IGCSE)
Q = It | moles of e⁻ = Q/F | moles of product = moles of e⁻ / n | mass = mol × Mr