How to soften:
-Remove the calcium and magnesium ions by:
a) Add sodium carbonate
b) Ion exchange columns
Permanent
Remains hard when boiled
Temporary
Softened when boiled
Contains hydrogencarbonate ions (HCO3).
These decompose on heating to produce
carbonate ions which react with calcium and
magnesium ions to form precipitates.
Disadvantages
More expensive
Causes limescale which reduces
efficiency of electrical appliances