Question

a chemical reaction which is both combination as well as exothermic is used by us for white washing purpose write the equation for the same?

Answer 1

Calcium oxide ( Quick lime) reacts with water to form Calcium Hydroxide and lot of heat .
As two two elements are reacting to produce only one product. This type of reaction is called as Chemical combination reaction.
During the chemical reaction, lot of heat is produced . Hence it is exothermic reaction.
BALANCED CHEMICAL Equation:
CaO (s) + H2O(l) ----> Ca (OH)2(aq) +Q
Here, calcium hdroxide (Slaked lime) is generally used for white washing.
After 2 or 3 days of white wash , the wall will get shine and white colour due to the following reaction:
Ca (OH)2 + CO2----> CaCO3(s) + H2O

Answer 2

"Calcium hydroxide which is also called as "slaked lime" which is generally used for "white washing". The formation of slaked lime from quicklime and water is an exothermic reaction as well as combination reaction.

$CaO(s)\quad +\quad { H }_{ 2 }O(l)\quad \longrightarrow \quad Ca{ \left( OH \right)  }_{ 2 }(aq)\quad +\quad Heat$

Here, CaO or quicklime and water mix to form "calcium hydroxide", therefore it is a combination reaction and heat is released which makes it a exothermic reaction.

This chemical reaction can be used for manufacturing of slaked lime."