Two liquids A and B form an ideal solution. At a certain temperature, the vapour pressure of pure A is 100 mm Hg and of pure B is 300 mm Hg. A solution containing 1 mol of A and 3 mol of B has total vapour pressure:
A150 mm Hg
B200 mm Hg
C300 mm Hg
D250 mm Hg
Answer & Solution
Correct answer: D. 250 mm Hg
$x_A = 0.25$, $x_B = 0.75$. By Raoult's law $P = x_A P_A^0 + x_B P_B^0 = 0.25(100) + 0.75(300) = 25 + 225 = 250$ mm Hg.
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