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Differentiate between temporary and permanent hardness.
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written 3.6 years ago by |
Temporary Hardness | Permanent Hardness |
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Temporary hardness can be removed simply by boiling the water (see later). | Permanent hardness cannot be removed by boiling but can often be removed by chemical treatment (see later). |
Temporary hardness is caused by calcium and/or magnesium hydrogencarbonate. These are formed as carbonated rain water passes over rocks containing carbonate ions, for example: |
$H_2O(l) + CO_2(g) + CaCO_3(s)\rightarrow Ca(HCO_3)_2(aq)$$H_2O(l) + CO_2(g) + MgCO_3(s) \rightarrow Mg(HCO_3)_2(aq)$ | Permanent hardness is caused by calcium and/or magnesium sulphate. These are formed as water passes over rocks containing sulphate ions, for example $aq. + CaSO_4(s)\rightarrow Ca^{2+}(aq) + SO_4^{2-}(aq)$$aq. + MgSO_4(s)\rightarrow Mg^{2+}(aq) + SO_4^{2-}(aq)$ |