試題詳解

40. Liquid A has vapor pressure x. Liquid B has vapor pressure y, and x ＞ y. What is the mole fraction of A in the liquid mixture if the vapor above the solution is 50% A?
(A) y/(2x + 2y)
(B) y/(x+ y)
(C) x/(2x + 2y)
(D) x/(x + y)
(E) none of these