Question

Why in the laboratory preparation of hydrochloric acid the temperature of the reaction mixture is kept below 200 degree?

Answer 1

Sodium bisulphate reacts with common salt to form sodium
sulphate. The sodium sulphate so formed fuses in glass
apparatus and renders it useless.
NaHSO4 + NaCl Diffused ⎯⎯⎯→ light Na2SO4 + HCl

Answer 2

In the laboratory preparation of hydrochloric acid the temperature of the reaction mixture is kept below 200°, because -

• We can prepare hydrochloric acid in the laboratories by the chemical reaction of sodium chloride salt and sulfuric acid.
• The production of the hydrochloric acid above 200° becomes more rapid than the production of hydrochloric acid below 200°.
• But, still the production is performed under 200°, because produced sodium sulfate is very difficult to remove from the glass apparatus and the glass apparatus can also get damaged by the high amount of heat energy application.