Washing soda can be used for softening hard water.

Answer the following:

A calcium compound having odour of chlorine is used to remove yellowish-white clothes in laundries. Name the compound.

What is gypsum? What happens when gypsum is heated to $373\mathrm{K}$?

Answer the following:

Write the formula of a salt that contains water of crystsllisation.

What are $\mathrm{X}$ and $\mathrm{Y}$, respectively in the following reactions ?

$\mathrm{Au}+\mathrm{aqua} \mathrm{regia}⟶{\mathrm{AuCl}}_4^{-}+{\mathrm{H}}_2\mathrm{O}+\mathrm{X}$

$\mathrm{Pt}+\mathrm{aqua} \mathrm{regia}⟶{\mathrm{PtCl}}_6^{2-}+{\mathrm{H}}_2\mathrm{O}+\mathrm{Y}$

State:

The difference between number of molecules in Gypsum and in Plaster of Paris.

Write the chemical formulae of the following:

(a) Common salt  (b) Slaked lime (c) Bleaching powder.

Which of the following statements is correct?