Chemistry · The vapour pressure of solutions and Raoult's Law - Ideal and non-ideal solutions, vapour pressure composition, plots for ideal and non-ideal solutions
The vapour pressures of two liquids and B in their pure states are in the ratio
The vapour pressures of two liquids \( A \) and B in their pure states are in the ratio of \( 1: 2 . \) A binary solution of \( A \) and \( B \) contains \( A \) and \( B \) in the mole proportion of \( 1: 2 . \) The mole fraction of \( A \) in the vapour phase of the solution will be:
- A. 0.33
- B. 0.2
- C. 0.25
- D. 0.52
Step-by-step solution
Given ratio of pure vapor pressures P_A^0 : P_B^0 = 1:2, let P_A^0 = P, P_B^0 = 2P. In liquid, mole fractions from proportion 1:2 are x_A = 1/3, x_B = 2/3. By Raoult's law, partial pressures: p_A = (1/3)P, p_B = (2/3)*2P = (4/3)P. Total pressure = (5/3)P. Vapor mole fraction y_A = p_A / P_total = (1/3)/(5/3) = 1/5 = 0.20.
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