Fractional distillation of Air (1 Viewer)

Eagle Mum

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Fractional distillation is based on different boiling points of individual gases. The boiling point of nitrogen is -196 degC, so that’s the temperature at which the nitrogen gas will turn to liquid and can be poured off.

The only equation I can think of would be the enthalpy balance equation:
1637364562983.png The value of the latent heat of vaporisation of the nitrogen (N2) molecule is 5.59 kJ/mol

You may otherwise be thinking of an equation for estimating the fraction of nitrogen in atmospheric air. For oxygen, which is highly reactive, its reaction with copper, with subsequent loss of the mass of solid copper is used to estimate the fraction of oxygen. Since the nitrogen molecule is relatively inert, the nitrogen fraction is estimated as the residual fraction, however the reaction equation for the Haber process would be applicable as the amount of nitrogen can be calculated from measuring the amount of ammonia produced.
 

wizzkids

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Physical Chemistry isn't really a syllabus topic. There isn't really an equation, because it's not a chemical change, it's a physical change. The industrial process for the manufacture of pure liquid oxygen and liquid nitrogen starts with liquid air, which contains 20% O2 and 79% N2 and about 1% Ar.
Liquid air exists in equilibrium with a partial pressure of nitrogen gas and partial pressure of oxygen gas. Oxygen boils at -183 deg C, nitrogen boils at -196 deg C. By gently warming liquid air, at -196 deg C, the gas phase coming off will be almost pure gaseous nitrogen. When the remaining liquid is sufficiently enriched in oxygen, the boiling point gradually rises and in another multi-stage separation, a pure liquid oxygen fraction is separated by fractional distillation.
 

CM_Tutor

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so its not 2H2(l) + O2(g) + N2 (g) --> 2H2(g) + N2(g)??
No, because that equation suggests that there is hydrogen liquid present, which is not present in liquid air and would need a much lower temperature, and it sees oxygen just vanish and so is unbalanced.
 

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