Question

Ingredients used in kitchens always amazes us through their magic. One of them is 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 in ant bite. In the laboratory, when we heat compound X, it gets converted into Y which is anhydrous but absorbs water to become a hydrated salt Z, one of the raw materials of soaps and detergents.

(ii) Identify the compound Y and Z from the following:

• A. Y: $NaHC{O}_3$, Z: $N{a}_{2}C{O}_3.10H_{2}O$
• B. Y: $N{a}_{2}C{O}_3$, Z: $N{a}_{2}C{O}_3.10H_{2}O$
• C. Y: $NaOH$, Z: $NaCl$
• D. Y: $NaHC{O}_3$, Z: $N{a}_{2}C{O}_3$

Answer 1

The correct option is B Y: $N{a}_{2}C{O}_3$, Z: $N{a}_{2}C{O}_3.10H_{2}O$

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 $\left(N{a}_{2}C{O}_3\right)$ which is anhydrous in nature i.e. no water molecule attached to the molecule of sodium carbonate.
Sodium carbonate when comes in contact with moisture, it get hydrated with 10 molecules of water to form sodium carbonate decahydrate $\left(N{a}_{2}C{O}_3.10H_{2}O\right)$.
Thus, Z is sodium carbonate decahydrate $\left(N{a}_{2}C{O}_3.10H_{2}O\right)$ which is commonly known as washing soda, a raw material used in soap and detergent manufacturing.