At 50∘C, liquid A has a vapor pressure of 237

Question

At 50∘C, liquid A has a vapor pressure of 237 torr and liquid B has a vapor pressure of 341 torr. If 5.50 moles of liquid A and 6.00 moles of liquid B are combined to form an ideal solution, what is the vapor pressure above the solution at 50.0∘C?

Answer 1

Assuming ideal mixture, and using Raoult's Law:

P_A = X_AP^o_A (partial pressure A = mole fraction A x vapor pressure pure A)

P_B = X_BP^o_B (partial pressure B = mole fraction B x vapor pressure pure B)

P_total = P_A + P_B (Total pressure = partial pressure A + partial pressure B)

moles A = 5.50 and moles B = 6.00. Total moles =11.50

mole fraction A = 5.50/11.50 = 0.478

mole fraction B = 6.00/11.50 = 0.522

P_A = 0.478 x 237 torr = 113.3 torr

P_B = 0.522 x 341 torr = 178.0 torr

P_total = 113.3 torr + 178.0 torr = 291.3 torr