The Vapor pressures of pure propyl alcohol and isopropyl alcohol are 21.0 mmHg and 45.2 mmHg, respectively, at 25 (degrees)C. Calculate the partial pressure of isopropyl alcohol above a solution in which the mole fraction of propyl alchol is 0.250.

Answer 1

P_soln = X_ip*P^o_ip

Xpropyl = 0.250; therefore, Xipropyl = 0.750
Plug into the above.
Check my thinking.