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ICSE Class 10 Chemistry Question 14 of 53

Study of Compounds — Hydrogen Chloride — Question 12

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Question

Question 12

The following questions pertain to the laboratory preparation of hydrogen chloride gas:

(a) Write the equation for it's preparation mentioning the conditions required.

(b) Name the drying agent used in the above preparation and give a reason for the choice.

(c) State a safety precaution taken during the preparation of hydrochloric acid.

Answer

(a) The equation for the laboratory preparation of hydrogen chloride gas :

NaCl+H2SO4→<200°CNaHSO4+HCl [g]\text{NaCl} + \text{H}_2\text{SO}_4 \xrightarrow{\lt 200 \degree\text{C}} \text{NaHSO}_4 + \text{HCl [g]} ↑

(b) Concentrated sulphuric acid is used as the drying agent used in the above preparation.

Reason — Drying agent used for drying should only remove the moisture and not react with it, hence, conc. sulphuric acid is used as the drying agent. Other drying agents like phosphorous pentoxide (P2O5) and quick lime (CaO) cannot be used since they react with hydrogen chloride gas.

(c) Temperature is maintained at nearly 200°C as at higher temperatures above 200°C the glass apparatus may crack, fuel is wasted, sodium sulphate formed, forms a hard crust which sticks to the glass and is difficult to remove.