mole fraction

[mikep]

does anyone know how to do this problem?
The total vapor pressure above a solution of C_6H_6(l) and C_7H_8(l) is 0.485 atm. What is the mole fraction of C_6H_6(l) in the liquid solution?
P^o C6H6(l) = 0.526 atm
P^o C7H8(l) = 0.188 atm

the answer is 0.879 but i'm not sure how to get that using the formula P_A = (X_A)(P^o _A)

[Gokul43201]

does anyone know how to do this problem?
The total vapor pressure above a solution of C_6H_6(l) and C_7H_8(l) is 0.485 atm. What is the mole fraction of C_6H_6(l) in the liquid solution?
P^o C6H6(l) = 0.526 atm
P^o C7H8(l) = 0.188 atm

the answer is 0.879 but i'm not sure how to get that using the formula P_A = (X_A)(P^o _A)

It's a direct substitution problem.

P_{tot} = P_A + P_B = (X_A)(P^o _A) + (X_B)(P^o _B) = (X_A)(P^o _A) + (1-X_A)(P^o _B)

Now just plug in the given numbers and solve for X_A