Question

Ingredients used in kitchens always amaze us through their magic. One of them is a baking powder which has a compound X as its major constituent. The compound X sometimes also helps in getting relief from acid indigestion or even ant bite. In the laboratory, when we heat compound X, it gets converted into Y (a sodium compound) and also results in the evolution of a gas G which turns limewater milky.

a) Identify the compound X.
b) Identify the compounds Y and G. Write the balanced chemical equation for the heating of compound X.
c) What will happen if we dip red litmus paper into the aqueous solution of Y? Justify the reason behind it.

Answer 1

a) In the kitchen, baking powder is used as an ingredient for making tasty pakodas, fluffy cakes and more.
Baking powder has baking soda $(NaHC{O}_3$) as a major constituent along with some edible acids into it.
Therefore, compound X is $NaHC{O}_3$: a mild base.
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b) Heating of baking soda $\left(NaHC{O}_3\right)$ results in the formation of sodium carbonate $\left(N{a}_{2}C{O}_3\right)$ and carbon dioxide gas along with water vapours.
Hence, Y is sodium carbonate $\left(N{a}_{2}C{O}_3\right)$ and G is carbon dioxide $\left(C{O}_2\right)$ respectively.
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The balanced chemical equation for heating of sodium bicarbonate is as follows:


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c) When a small amount of sodium carbonate is added to water, the pH of the water increases above 7. Therefore, the solution becomes basic and changes the colour of red litmus paper to blue.
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The pH of distilled water is 7. So, the water is neutral before adding sodium carbonate. The pH value for sodium carbonate is around 11, hence it is basic in nature. Adding a small amount of sodium carbonate into water increase the pH above to 7. Being a basic solution, aqueous solution of sodium bicarbonate changes the colour of red litmus paper to blue.
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