Question

Write the preparation of following compounds with balanced chemical equation :
Baking soda
Bleaching powder
Plaster of Paris

Hint:

For Plaster of Paris, if the temperature exceeds \( 373 \text{ K} \), it forms 'dead burnt plaster' (\( CaSO_4 \)) which lacks setting properties.

Answer 1

Step 1: Detailed Explanation:
(i) Baking Soda (Sodium hydrogen carbonate, \( NaHCO_3 \)): Produced using the Solvay process by reacting cold and concentrated sodium chloride (brine) with ammonia and carbon dioxide.
\[ NaCl + H_2O + CO_2 + NH_3 \rightarrow NH_4Cl + NaHCO_3 \]
(ii) Bleaching Powder (Calcium oxychloride, \( CaOCl_2 \)): Prepared by the action of chlorine gas on dry slaked lime.
\[ Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O \]
(iii) Plaster of Paris (Calcium sulphate hemihydrate, \( CaSO_4 \cdot \frac{1}{2}H_2O \)): Prepared by heating gypsum (\( CaSO_4 \cdot 2H_2O \)) to \( 373 \text{ K} \) (\( 100^\circ\text{C} \)) in a kiln. At this temperature, it loses three-fourths of its water of crystallization.
\[ CaSO_4 \cdot 2H_2O \xrightarrow{373 \text{ K}} CaSO_4 \cdot \frac{1}{2}H_2O + 1\frac{1}{2}H_2O \]
Step 2: Final Answer:
The balanced equations for preparation are:
(i) \( NaCl + H_2O + CO_2 + NH_3 \rightarrow NH_4Cl + NaHCO_3 \)
(ii) \( Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O \)
(iii) \( CaSO_4 \cdot 2H_2O \xrightarrow{373 \text{ K}} CaSO_4 \cdot \frac{1}{2}H_2O + 1.5H_2O \)