Question

Methane is heated from 27.0 ºC to 63.0 ºC at constant pressure. Calculate ΔU and ΔH. Assume that methane is an ideal gas. (CV= 5.82 + (7.55 x 10-2)T - (17.99 x 10-6)T2 J K-1 mol-1).

Answer 1

Since pressure is constant this is an isobaric process.

Given dT = 63.0 C - 27.0 C = 36.0 C

Given Cv = 5.82 + (7.55 x 10-2)T - (17.99 x 10-6)T2 J K-1 mol-1

Now  U can be calculated from the following relation.

U = 1008.3 J/mol

Cp = Cv + R = [5.82 + (7.55 x 10-2)T - (17.99 x 10-6)T2 J K-1 mol-1] + 8.314 JK-1mol-1

=> Cp = [14.134 +(7.55 x 10-2)T - (17.99 x 10-6)T2 J K-1 mol-1]

Hence H = 1307.6 J/mol