Question

A compound ‘X’ on heating at \(373 \, \text{K}\) loses water molecules and becomes ‘Y’. Substance ‘Y’ is used by doctors for supporting fractured bones in the right position.

1. Identify ‘X’ and ‘Y’.
2. How can we obtain ‘X’ from ‘Y’?

Answer 1

1. Identify ‘X’ and ‘Y’:
The compound 'X' is gypsum (CaSO₄·2H₂O). When heated at \( 373 \, \text{K} \), gypsum loses water molecules and becomes 'Y', which is plaster of Paris (CaSO₄·½H₂O).
Plaster of Paris (Y) is commonly used by doctors for supporting fractured bones in the right position, as it hardens when mixed with water and forms a strong cast.

2. How can we obtain ‘X’ from ‘Y’?
To obtain 'X' (gypsum) from 'Y' (plaster of Paris), we need to add water to plaster of Paris. The reaction is as follows:
\[ \text{CaSO}_4 \cdot \frac{1}{2} \text{H}_2\text{O (Plaster of Paris)} + \text{H}_2\text{O} \rightarrow \text{CaSO}_4 \cdot 2\text{H}_2\text{O (Gypsum)} \] By adding water to plaster of Paris, it rehydrates to form gypsum, which is the original compound before it was heated to form plaster of Paris.