Question

The temporary hardness of water can be removed by Clark's Method using _____. [1mark]
A. $NaCl$
B. $NaOH$
C. $N{a}_{2}C{O}_3$
D. $Ca(OH{)}_2$

Answer 1

Correct answer: Option D. $Ca(OH{)}_2$

Temporary hardness is due to the presence of bicarbonates of Calcium and Magnesium. Both these, when treated with $Ca(OH{)}_2$, precipitate $C{a}^{2+}$ and $M{g}^{2+}$ as insoluble carbonates, which can then be filtered out. This is called Clark's method.