Question

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Answer 1

How is white washing done?
# First step in white washing is mixing CaO with excess of water, in presence of oxygen. It is a highly exothermic process and.large amount of heat is given out.

Chemical reaction: CaO+H2O =＞ Ca(OH)2 + heat

#.secound step This Ca(OH)2 is coated on the walls of the building. The Ca(OH)2 present in the wall reacts with the CO2 present in the atmosphere to form CaCO3,which is white in colour,it quite a slow process and hence takes atleast two days.

Chemical reaction =＞Ca(OH)2+CO2 =＞ CaCO3 + H2O

The above reaction takes place during white washing

NOTE:
1.CaO is also called as quick lime
2.Ca(OH)2 is also called as slacked lime
3.CaCO3 is also called as limestone.

Answer 2

Answer:

Hey, i know that this question is 3 years old now but i am interest to answer it)

Calcium Hydroxide is formed when water and calcium oxide are combined together .

CaO + H₂O ===> Ca(OH)₂  

When Calcium hydroxide is painted on the walls , and left for 2 days , a layer of calcium carbonate is formed on the walls , which gives a white and shiny appearance to the walls.This is because of the reaction of calcium hydroxide with carbon dioxide to form calcium carbonate and water.

Ca(OH)₂ + CO₂ ==> CaCO₃ + H₂O