Question

Which statement explains why oxygen can be separated from nitrogen by the fractional distillation of liquid air?
A)Oxygen is more dense than nitrogen
B)Oxygen is more reactive than nitrogen
C)The two elements have different boiling point
D)The two gases are in different groups of the periodic table.

Answer 1

The liquid air basically undergoes a process called fractional distillation. It generally uses the different boiling points of the main elements of air. Moreover, at this point, the carbon dioxide will become solid and leaves oxygen, nitrogen and argon in the air.

Complete step by step answer:
The air in the Earth’s atmosphere consists of nitrogen, argon, oxygen, carbon dioxide and many other gases. So, basically to separate the sample of air into its primary components, the scientists need to cool the air more, and this process is further known as fractional distillation of liquid air. Further, it requires an air separation unit which is not unlike a conventional distillation tube used for purifying water.
Now, each gas has a significant boiling point which is defined as the temperature at which it transforms from a liquid into a gas and if you have a random sample of gases, then you can separate them by gradually cooling the sample until the gas of each component liquefies. Thereafter, the liquefied compound falls to the bottom of a collective vessel and after all of the liquid has been retrieved, the cooling continues until the temperature drops to the boiling point of the next compound. Some compounds such as carbon dioxide never liquefy.
So, oxygen can be separated from nitrogen by fractional distillation of liquid air because the two elements have different boiling points.
Hence, option C is correct.

Note: The separation of gases by fractional distillation isn’t the only way to generate oxygen or nitrogen from air. However, a membrane generator uses a system of semipermeable, hollow fiber membrane that allows smaller molecules in a sample of compressed air to pass while blocking the larger ones.