Question

A solution of substance X used for white washing.Write the chemical name and formula of X . Also write the reaction of X with water

Answer 1

The substance used for white washing is calcium oxide.
Calcium oxide is also known as quicklime or burnt lime.
Calcium oxide is an oderless substance.
It's density is 3.34 g/cm³.
It's boiling point is 2,850 °C.
It's melting point is 2,613 °C.
The formula of Calcium oxide is CaO
Ffter Calcium oxide reacts with water it becomes 
CaO + H₂O ---->Ca (OH)₂  + heat

Answer 2

 (i) The substance X is lime which is used for white washing. Its formula is CaO.
(ii) CaO + H2O –––> Ca(OH)2 + Heat