Question

Baking soda is used in small amount in making bread and cake. It helps to make these soft and spongy. An aqueous solution of baking soda turns red litmus blue. It is also used in soda acid fire extinguisher.
Use this information to answer the following questions:
(a) How does baking soda help to make cakes and bread soft and spongy?
(b) How does it help in extinguishing fire?
​(c) Is the pH value of baking soda solution lesser than or greater than 7?

Answer 1

(a) Baking soda reacts with the acidic ingredients of bread and cake to form carbon dioxide gas which makes the foodstuff to rise and thus makes it soft and spongy.

(b) Soda acid fire extinguishers contain a mixture of sulphuric acid and baking soda. They react to release carbon dioxide which forms a layer over the burning substance and cuts the supply of oxygen of the fire.
${\mathrm{NaHCO}}_3+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Na}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}+2{\mathrm{CO}}_2$

(c) The pH of baking soda solution is greater than 7 since, it is a salt of a strong base, NaOH and a weak acid, H₂CO₃.