Liquefied air is mainly a mixture of nitrogen and oxygen which can be separated into its components by fractional distillation (Boiling point of nitrogen is...
Question 1 Report
Liquefied air is mainly a mixture of nitrogen and oxygen which can be separated into its components by fractional distillation (Boiling point of nitrogen is 196°C, Boiling point of oxygen is 174°C)
(a) Name the fraction which distills over first. Give the reason for your answer.
(b) Give another industrial application of fractional distillation as a separation technique.
Answer Details
(a) Fraction that distills over first
The fraction that distills over first is nitrogen.
Reason: Fractional distillation separates the components according to their boiling points, the component with the lower boiling point (the more volatile one) boiling off and distilling over first. Nitrogen has a lower boiling point (about \(-196\,^{\circ}C\)) than oxygen (about \(-183\,^{\circ}C\)). Therefore, as the liquefied air warms up, nitrogen reaches its boiling point first, vaporizes and distills over before oxygen.
(b) Another industrial application of fractional distillation
Fractional distillation is used in the refining of petroleum (crude oil), where crude oil is separated into useful fractions such as petrol, kerosene, diesel and lubricating oil according to their different boiling ranges. (It is also used to separate ethanol from a fermented ethanol-water mixture.)
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