For an ideal binary mixture of liquids A and B, the plot of the reciprocal of total vapour pressure ( 1 P_ total ) against the vapour phase mole fraction of A ( y_A ) is a straight line. The intercepts on the y-axis at y_A = 0 and y_A = 1 are 0.01 torr ⁻¹ and 0.005 torr ⁻¹ , respectively. The total vapour pressure of the solution (in torr) when the liquid phase mole fraction of A ( x_A ) is 0.4 will be:

Step-by-step solution

According to Dalton's and Raoult's laws, the total pressure in terms of vapour phase mole fractions is given by: 1 P_ total = y_A P_A^0 + y_B P_B^0 = y_A P_A^0 + 1-y_A P_B^0 At y_A = 0 , the mixture is pure B. The intercept is 1 P_B^0 = 0.01 torr ⁻¹ , which gives P_B^0 = 100 torr. At y_A = 1 , the mixture is pure A. The intercept is 1 P_A^0 = 0.005 torr ⁻¹ , which gives P_A^0 = 200 torr. To find the total vapour pressure when the liquid phase mole fraction x_A = 0.4 , we use Raoult's law: P_ total = x_A P_A^0 + x_B