Question

how does CAO gives shiny appearance ?

Answer 1

Dear student
When CaO is added to water, it forms Ca(OH)2 and releases heat according to the reaction given below:
CaO + H₂O$\to$ Ca(OH)₂ + Heat

This Calcium hydroxide solution is applied to the walls of the house , then it reacts with the Carbon dioxide present in the air to give a thin , shining layer of Calcium carbonate on the walls of the house.
Since this process gives a white, shining appearance to the walls , it is called White-Washing. The chemical reaction taking place is as follows:
Ca(OH)₂ (aq) + CO₂(g) $\to$ CaCO₃ (s) + H₂O(l)

Regards