For an ideal solution of A and B, Y_A is the mole fraction of A in the vapour phase at equilibrium. — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

In an ideal solution, the relationship between total pressure and vapour phase mole fraction is given by: 1 / P_total = Y_A / P_A^o + Y_B / P_B^o. Since Y_B = 1 - Y_A: 1 / P_total = Y_A / P_A^o + (1 - Y_A) / P_B^o = Y_A * (1 / P_A^o - 1 / P_B^o) + 1 / P_B^o. This is a linear equation of the form y = m*x + c, where y = 1 / P_total and x = Y_A. Therefore, the plot of 1 / P_total vs Y_A is linear.