Salt A commonly used in bakery products on heatein gets converted in to another salt B which itself is used for removal of hardness of water and a gas c is evolved . The gas c when passsed thourgh lime water turns it milky. Identify A,B and C.

Explanation

The salt 'A' is sodium hydrogen coarbonate (baking soda) and is commonly used in bakeries as a constitutent of baking power. Upon heating, it change to sodium carbonate 'B' and evolves carbon dioxide gas 'C'.
`underset('A')(2NaHCO_(3)) overset("heat")to underset('B')(Na_(2))CO_(3)+underset('C')(CO_(2))`
Sodium carbonate removes hardness from water while `CO_(2)` gas turns lime water milky. For more details, consult section 0.12.