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) The compound X:
(a) Sodium carbonate (b) Sodium bicarbonate
(b) Sodium oxide (d) Nitric acid
[1 Mark]
(b) The compounds Y and G:
(a) Sodium carbonate and hydrogen
(b) Sodium bicarbonate and carbon dioxide
(c) Sodium bicarbonate and hydrogen
(d) Sodium nitrate and nitrogen dioxide
[1 Mark]
(c) State the reason behind the change in appearance of limewater when gas G is passed through it.
[1 Mark]
(d) Write the balanced chemical reaction involved when gas G is passed through limewater.
[1 Mark]

Answer 1

(a) Correct option is (b) i.e. sodium bicarbonate.
[1 Mark]
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 sodium bicarbonate $NaHC{O}_3$: a mild base.

(b) Correct option is (c) i.e. sodium bicarbonate and hydrogen
[1 Mark]
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.
The balanced chemical equation for heating of sodium bicarbonate is as follows:


(c) Limewater is basically calcium hydroxide solution. If carbon dioxide(${\text{CO}}_2$) passed through calcium hydroxide, it form calcium carbonate(${\text{CaCO}}_3$). Calcium carbonate obtained is white and insoluble in water, hence it makes limewater appear milky.
[1 Mark]

(d) The reaction involved is:
${\text{Ca(OH)}}_2\text{(aq)}+{\text{CO}}_2\text{(g)}\to {\text{CaCO}}_3\text{(s)}+{\text{H}}_2\text{O}\text{(l)}$
[1 Mark]