Question

Which one the following removes temporary hardness of water ?

• A. Slaked lime
• B. Plaster of Paris
• C. Epsom
• D. Hydrolith

Answer 1

Answer: (A)

Slaked lime

Answer 2

Temporary hardness is due to presence of bicarbonates of $Ca$ (II) and $Mg$ (II). Temporary hardness is removed by adding lime water or milk of lime. This method is known as Clark's process. Removal of hardness is called softening of water.
$Ca ( OH )_{2}+ Ca \left( HCO _{3}\right)_{2} \rightarrow 2 CaCO _{3} \downarrow+2 H _{2} O$