CBSE Class 10 Science 2019 · Paper 31/1/3/C · Question 3

Sodium hydrogen carbonate (${\text{NaHCO}}_3$) is the salt of a strong base, sodium hydroxide ($\text{NaOH}$), and a weak acid, carbonic acid (${\text{H}}_2{\text{CO}}_3$). The strong base outweighs the weak acid, so its solution in water is basic, with pH above $7$ (about $8.3$): it is an alkaline salt. Uses (any two): (i) In baking powder, to make cakes and bread soft and spongy, because it gives off carbon dioxide; (ii) As an antacid, to neutralise excess acid in the stomach; (iii) In soda-acid fire extinguishers.