Estimate the critical temperature and critical pressure for

Estimate the critical temperature and critical pressure for a mixture of 60 weight percent ethane and 40 weight percent n-heptane.

Here, we have ethane of 60% and n-heptane of 40% which lies between point 3 and point 4.

At point 3, At point 4,

Ethane = 70.22 % Ethane = 50.25 %

Pressure = 1200 psig Pressure = 1300 psig

Temperature = 200 deg F Temperature = 300 deg F

By interpolating,

(T - 200) / (300 - 200) = (60 - 70.22) / (50.25 - 70.22)

or, T = 251.177

The critical temperature for the said mixture is 251.177 deg F.

Again interpolating for pressure,

(P - 1200) / (1300 - 1200) = (60 - 70.22) / (50.25 - 70.22)

or, P = 1251.177

The critical pressure for the said mixture is 1251.177 psig.