A solution of two volatile components showing negative deviation from Raoult’s law shows:-

Correct Answer: Decrease in vapour pressure, boiling point increases

Step-by-Step Explanation:

To understand why this choice is correct, let us analyze the behavior of non-ideal solutions showing negative deviation from Raoult's law by breaking down the vapour pressure behavior and its direct effect on the boiling point:

1. Analysis of Vapour Pressure (Negative Deviation):
According to Raoult's law, in an ideal solution, the partial vapour pressure of each volatile component is directly proportional to its mole fraction. However, in non-ideal solutions exhibiting negative deviation, the intermolecular attractive forces between the two different components (A–B attractions) are stronger than the cohesive forces present within the pure components themselves (A–A and B–B attractions).
Since the components attract each other more strongly in the mixture than in their respective pure states, the molecules are held more tightly in the liquid phase and have a reduced tendency to escape into the gas phase. Consequently, the vapour pressure of the mixture decreases below the value predicted for an ideal solution.
This behaviour is visually confirmed by the provided graph. The graph plots V.P (Vapour Pressure) on the vertical y-axis against mole fractions on the horizontal x-axis, transitioning from
$$x_A=1,x_B=0$$
on the left to
$$x_A=0,x_B=1$$
on the right. The dashed straight lines represent the expected linear relationship for an ideal solution, while the solid curves sag downward beneath these dashed lines, representing the lower-than-expected vapour pressure that defines a negative deviation.

2. Effect on Boiling Point:
By definition, the boiling point of a liquid is the temperature at which its vapour pressure becomes equal to the external atmospheric pressure.
Since a solution with negative deviation has a lower vapour pressure at any given temperature compared to an ideal mixture, it must be heated to a higher temperature before its vapour pressure increases enough to equal the external atmospheric pressure. Therefore, the boiling point of such a solution increases (leading to the formation of a maximum boiling azeotrope at a specific composition).

Thus, a solution showing negative deviation from Raoult's law shows a decrease in vapour pressure, which directly leads to an increase in boiling point.