A mixture of potassium chlorate and potassium chloride weighing 20 g was heated. The mass of the mixture decreased by 4.8 g. What was the mass fraction of KCl in the original mixture?
- 38.75%
- 61.25%
- 50%
- 24%
📝 Detailed explanation
Only KClO₃ decomposes: 2KClO₃ → 2KCl + 3O₂.The mass loss is due to oxygen: 4.8 g.
Moles O₂ = 4.8 / 32 = 0.15 mol.
Moles KClO₃ = 0.15 × (2 / 3) = 0.1 mol.
Mass KClO₃ = 0.1 × 122.5 = 12.25 g.
Mass KCl = 20 - 12.25 = 7.75 g.
Mass fraction KCl = 7.75 / 20 = 0.3875 or 38.75%.