CBSE Class 10 Science 2018 · Paper 31/1/C · Question 7(b)

(a) The cake will taste bitter. On heating, baking soda (sodium hydrogencarbonate) decomposes and forms sodium carbonate, a base, which stays in the cake and gives it a bitter taste: $2{\text{NaHCO}}_3\stackrel{\text{heat}}{\to }{\text{Na}}_2{\text{CO}}_3+{\text{H}}_2\text{O}+{\text{CO}}_2$. (b) By mixing baking soda with a mild edible acid such as tartaric acid; the acid reacts with the sodium hydrogencarbonate, so no bitter sodium carbonate is formed. (c) Carbon dioxide, released when baking powder is heated or mixed with water (${\text{NaHCO}}_3+{\text{H}}^{+}\to {\text{CO}}_2+{\text{H}}_2\text{O}+\text{sodium salt of the acid}$), forms bubbles that make the cake rise, so it becomes soft and spongy.