Which type of water hardness can be removed by boiling?

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Prepare for the WJEC GCSE Chemistry Exam with multiple choice questions and detailed explanations. Enhance your knowledge and boost your confidence. Get exam-ready today!

Multiple Choice

Which type of water hardness can be removed by boiling?

Explanation:
Temporary hard water contains dissolved bicarbonates of calcium and magnesium. When you boil it, these bicarbonates break down and release carbon dioxide, causing the acids to form carbonates that precipitate out as solid scale. A typical reaction is Ca(HCO3)2 -> CaCO3(s) + CO2(g) + H2O(l). With the calcium and magnesium removed from solution, the water becomes softer. Permanent hard water, made from sulfates or chlorides of these ions, doesn’t decompose on heating, so boiling doesn’t remove it. Soft water already has low hardness, so boiling isn’t needed.

Temporary hard water contains dissolved bicarbonates of calcium and magnesium. When you boil it, these bicarbonates break down and release carbon dioxide, causing the acids to form carbonates that precipitate out as solid scale. A typical reaction is Ca(HCO3)2 -> CaCO3(s) + CO2(g) + H2O(l). With the calcium and magnesium removed from solution, the water becomes softer. Permanent hard water, made from sulfates or chlorides of these ions, doesn’t decompose on heating, so boiling doesn’t remove it. Soft water already has low hardness, so boiling isn’t needed.

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