A compound X of sodium is commonly used in kitchen for making crispy pakoras

A compound X of sodium is commonly used in kitchen for making crispy pakoras.It is also used for curing acidity in the stomach. Identify X. What is its chemical formula? State the reaction which takes place when it is heated during cooking.

X = Sodium bicarbonate or sodium hydrogen carbonate.
Its formula is NaHCO3.
The reaction involved is: