Practice question

Given: A solution of two volatile liquids A and B has a total vapor pressure of 290 mm Hg. If the vapor pressure of pure A is 450 mm Hg and that of pure B is 150 mm Hg, what is the mole fraction of A in the solution? These values define the system as per NCERT data. Formula: Using Raoult's law: p_{total = x_A p_A⁰ + (1 - x_A) p_B⁰. This is standard NCERT relation. Substitution & Calculation: 290 = x_A · 450 + (1 - x_A) · 150 . 290 = 450 x_A + 150 - 150 x_A . 140 = 300 x_A, x_A = 0.467 . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.