Eduprobe
Question:
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):
The point Z represents vapour pressure of pure liquid M and Raoult's law is obeyed when xL→0
The point Z represents vapour pressure of pure liquid M and Raoult's law is obeyed from xL=0 to xL=1
The point Z represents vapour pressure of pure liquid L and Raoult's law is obeyed when xL→1
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
The point Z represents vapour pressure of pure liquid M and Raoult's law is obeyed when xL→0
The point Z represents vapour pressure of pure liquid M and Raoult's law is obeyed from xL=0 to xL=1
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
The point Z represents vapour pressure of pure liquid L and Raoult's law is obeyed when xL→1
Solution:
We know for Raoult's law P = P0LxL + P0MxM
Vapour pressure of L = PL = P0LxL = P0L(1-xM), at xM→0 or xL→1
PL = P0L which follows the graph shown at point Z
Line YZ forms tangent at a point Z which tells that it follows Raoult's law.
∴ option D is correct.
Let point P' show vapor pressure of mixture and point P'' shows vapor pressure of the ideal mixture.
Since P' > P'', it tells that in mixture L-M bonds break easily than that in the pure state as the vapour pressure of the mixture is more than it should be more in an ideal state.
Hence, option C is correct.