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

Preparation of the Following Compounds with Balanced Chemical Equations:

1. Baking Soda (Sodium Hydrogen Carbonate – NaHCO₃):

Baking soda is prepared by passing carbon dioxide gas through a solution of sodium chloride (brine) saturated with ammonia. This is a part of the Solvay process. Balanced chemical equation: \[ NaCl + NH_3 + H_2O + CO_2 \rightarrow NaHCO_3 + NH_4Cl \] In this reaction: – Sodium hydrogen carbonate (baking soda) is formed as a precipitate. 
– Ammonium chloride is formed as a by-product. 

2. Bleaching Powder (Calcium Oxychloride – CaOCl₂):

Bleaching powder is prepared by passing chlorine gas over dry slaked lime (calcium hydroxide). Balanced chemical equation: \[ Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O \] In this reaction: – Chlorine reacts with calcium hydroxide to form bleaching powder and water. 

3. Plaster of Paris (Calcium Sulphate Hemihydrate –\( CaSO₄·\frac{1}{2}H_2O):\)

Plaster of Paris is prepared by heating gypsum (calcium sulphate dihydrate) at about 100–120°C. Balanced chemical equation: \[ CaSO_4 \cdot 2H_2O \xrightarrow{\text{heat}} CaSO_4 \cdot \frac{1}{2}H_2O + \frac{3}{2}H_2O \] In this reaction: – Gypsum loses water molecules on heating. 
– Plaster of Paris is formed along with water vapour. 

Conclusion:
Baking soda is prepared by the Solvay process, bleaching powder is obtained by passing chlorine over slaked lime, and plaster of Paris is formed by heating gypsum. Each preparation involves a specific chemical reaction under controlled conditions.