Consider the following experimental set-up. (i) Identify by name: P; Q; R; S and T. (ii) State the method of collection of gas, S. (iii) What is the functio...

Answer Details

(i) Identification of the labelled parts:

• P - Delivery tube
• Q - Drying tower
• R - Calcium oxide (quicklime)
• S - Ammonia gas
• T - Retort stand with clamp

(ii) Method of collection of gas S: Ammonia is collected by upward delivery (downward displacement of air), because it is less dense than air and is very soluble in water.

(iii) Function of R (calcium oxide): It dries the gas, removing water vapour from the ammonia before collection. Calcium oxide is used because it does not react with ammonia (an acidic drying agent such as concentrated H₂SO₄ or anhydrous CaCl₂ would react with it).

(iv) Balanced equation for the preparation of gas S:

Ca(OH)_2(aq) + 2NH₄Cl_(aq) → CaCl_2(aq) + 2H₂O_(l) + 2NH_3(g)