Salt 'P', commonly used in bakery products, on heating gets converted into another salt 'Q' which itself is used for the removal of hardness of water and a gas 'R' is evolved. The gas 'R' when passed through freshly prepared lime water turns milky. Identify 'P', 'Q' and 'R', giving chemical equation for the justification of your answer.

Explanation

When baking solda, ` NaHCO_ 3 ` ( useed in baking products ) is heated or mixed in water the following reaction takes place -
` 2NaHCO_ 3 overset ("Heat") to Na_ 2 CO_ 3 + H_ 2 O + CO _ 2 `
Sodium carbonate is used to remove hardness of water. The gas evolved is carbon dioxide which turns lime water milky.
Therefore,
Salt 'P' is ` NaHCO _ 3 ` ( Sodium Hydrogen Carbonate ), which is used as baking powder.
Salt 'Q' is ` Na_ 2 CO_3 ` (Sodium Carbonate ), which is used to remove the hardness of water.
Gas 'R' is ` CO _ 2 ` (Carbon dioxide ) , which tuns lime water milky.