Question

Dry nitrogen gas cannot be collected by the displacement of ___________

Answer 1

Dry nitrogen gas is chemically inert, safe (if handled properly) and economic. Dry nitrogen gas is even used for purging to remove moisture or water vapour as well as oxygen to create a dry environment within a system or equipment.

Complete step by step answer:
The method to collect a gas being produced via a chemical reaction depends upon the density and solubility of gas. A gas can displace air only in case the gas is more dense in comparison to air. Since the density of air as well as nitrogen gas is almost similar, dry nitrogen gas cannot be collected by the displacement of air.
Dry nitrogen gas is insoluble in water so it can be collected by water displacement. It can be separated by fractional distillation of liquid air. Since air comprises 78% of nitrogen and 21% of oxygen, fractional distillation of liquid air can be performed to collect nitrogen. In simpler terms, the process of fractional distillation involves four steps:
-Cooling of the liquid air
-Isolation of the nitrogen gas
-Separation of nitrogen gas from the air
-Collection of the nitrogen gas
-At low temperature, nitrogen becomes liquid so it can then be extracted.

Hence, the correct answer is air.

Note:
In fractional distillation, the gas possessing the lowest boiling point (means highly volatile) will distil out first while the gas possessing the highest boiling point (means least volatile) will distil out at the last. Thus, nitrogen will distil out first and then oxygen during fractional distillation of liquid air.