Temporary Hard Water

• Temporary hard water is caused by dissolved calcium or magnesium hydrogen carbonate - when these hydrogen carbonate compounds are heated to boiling point if water, they thermally decompose:

  • Ca(HCO3)2 / Mg(HCO3)2 (aq) -> CaCO3 / MgCO3 (s) + H2O (l) + CO2 (g)
• Temporary hardness can be removed by boiling water, but results in formation of limescale.
• • Boiling water to remove temporary hardness doesn’t require special equipment and so is relatively cheap but only works for small volumes of water and won’t remove permanent hardness (removing permanent hardness will also remove temporary hardness).