Question

Common salt (NaCl) is not used as a raw material for preparation of which one of the following compounds?
1. Bleaching powder
2. Baking soda
3. Plaster of Paris
4. Washing soda

Answer 1

Correct Answer - Option 3 : Plaster of Paris

The correct answer is Plaster of Paris.

• Preparation of Plaster of Paris doesn't require the use of NaCl.
• It is simply obtained by heating gypsum (CaSO.2H O) at 120°C in a rotary kiln.
• Reaction involved: 2(CaSO₄.2H₂O) \(\longrightarrow\)  2(CaSO₄).H₂O + 2H₂O.

                                             (Gypsum)           (Plaster of Paris)  (Water)

• It turns in solid mass when mixed with water and hence used for plasterwork.​

• Bleaching powder is also called calcium chlorohypochlorite because it is considered a mixed salt of hydrochloric acid and hypochlorous acid. 
• Limestone and chlorine gas(produced from NaCl and HCl) are used as raw materials to manufacture bleaching powder which is used as a disinfectant and as an oxidizing agent.
• Raw materials needed for manufacturing baking soda are Sodium chloride, water, carbon dioxide, and ammonia.
• Balanced equation:- NaCl + H₂O + CO₂ + NH₃\(\longrightarrow\) NH₄Cl + NaHCO₃.

                                         (Sodium chloride)          (Ammonia)       (Baking soda/Sodium Bicarbonate)

 

• Sodium chloride (NaCl) and calcium carbonate (CaCO₃), are used as the raw materials for making washing soda using the Solvay process.
• The chemical equation of this reaction is: 2NaCl + CaCO₃\(\longrightarrow\) Na₂CO₃ + CaCl₂.
• Washing soda can also be formed by heating baking soda as 2NaHCO₃ \(\longrightarrow\) Na₂CO₃ + H₂O + CO₂.