Distillation is used to prepare 99 percent pure products from a mixture of n-butane and n-pentane. Vapor pressures are given below.

(a) Plot the vapor pressures in a form that permits accurate interpolation, and determine the average relative volatility for columns operating at 1, 2, and 8 atm. 

(b) Determine the minimum number of ideal plates for the separation at these three pressures. What is the main advantage of carrying out the separation at above atmospheric pressure?

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P, atm 0.526 1 2 5 10 20 Temperature, C n-C₂H₁0 <-16.3 -0.5 18.8 50.0 79.5 116.0 n-C₂H₁₂ 18.5 36.1 58.0 92.4 124.7 164.3