Ammonia is prepared by heating ammonium chloride with calcium hydroxide. It is dried by passing through calcium oxide and collected by upward delivery. i) Why is conc. sulphuric acid not used to dry a

here are the answers to question 7:

7. Ammonia is prepared by heating ammonium chloride with calcium hydroxide. It is dried by passing through calcium oxide and collected by upward delivery.

• i) Why is conc. sulphuric acid not used to dry ammonia gas? Ammonia ($\text{NH}_3$) is a basic gas, while concentrated sulphuric acid ($\text{H}_2\text{SO}_4$) is an acidic drying agent. They would react chemically to form ammonium sulphate, preventing the ammonia from being dried.

  $$\text{2NH}_3(g) + \text{H}_2\text{SO}_4(aq) \to (\text{NH}_4)_2\text{SO}_4(aq)$$ $$\boxed{\text{Ammonia is a basic gas and would react with acidic concentrated sulphuric acid.}}$$

• ii) Describe a chemical test for ammonia gas. A common chemical test for ammonia gas is to bring a damp piece of red litmus paper to the gas. Ammonia, being an alkaline gas, will turn the damp red litmus paper blue. Alternatively, bringing a glass rod dipped in concentrated hydrochloric acid near the gas will produce dense white fumes of ammonium chloride ($\text{NH}_4\text{Cl}$).

  $$\boxed{\text{Ammonia turns damp red litmus paper blue, or produces dense white fumes with HCl gas.}}$$

• iii) A student attempted to collect ammonia gas over water. Why did the student not succeed? Ammonia gas is highly soluble in water. If a student attempts to collect it over water, the ammonia gas will dissolve in the water instead of displacing it and being collected.

  $$\boxed{\text{Ammonia is highly soluble in water and would dissolve instead of being collected.}}$$