Question

It is possible to obtain oxygen from air by fractional distillation because
(a) oxygen is in a different group of the periodic table from nitrogen
(b) oxygen is more reactive than nitrogen
(c) oxygen has higher b.p. than nitrogen
(d) oxygen has a lower density than nitrogen

Answer 1

(c) Air is liquified by making use of the joule-Thompson effect (cooling by expansion of the gas) Water vapour and CO₂ are removed by solidification. The remaining major constituents of liquid air i.e., liquid oxygen and liquid nitrogen are separated by means of fractional distillation (b.p. of O₂ = –183°C : b. P. of N₂ = – 195.8°C)