For a solution formed by mixing liquids L and M, the vapour pressure of L plotted against the mole fraction of M in solution is shown in the following figure. Here xL and xM represent mole fractions of L and M, respectively, in the solution. The correct statement(s) applicable to this system is(are)
(A)The point Z represents vapour pressure of pure liquid M and Raoult's law is obeyed from xL=0 to xL=1
(B)The point Z represents vapour pressure of pure liquid L and Raoult's law is obeyed when xL→1✓ Correct
(C)The point Z represents vapour pressure of pure liquid M and Raoult's law is obeyed when xL→0
(D)Attractive intermolecular interactions between L-L in pure liquid L and M-M in pure liquid M are stronger than those between L-M when mixed in solution✓ Correct
Answer: (B), (D)
Solution
The graph shows positive deviation from Raoult's law. Point Z (at xM=0, i.e., xL=1) represents the vapour pressure of pure liquid L. Near xL→1, the solution obeys Raoult's law (the tangent matches the ideal line).
Positive deviation occurs when L-M interactions are weaker than L-L and M-M interactions in the pure liquids, meaning option D is correct.
Correct answers: B, D
JEE Advanced · 2017 · 21 May 2017 · Paper 1 · One or more correct options
