Question

Vapour pressure depends on:
(This question has multiple correct options)
A.Nature of the liquid
B.Temperature of the liquid
C.Area of the liquid
D.Volume of the liquid

Answer 1

Hint: We can define vapour pressure as the pressure exerted by gas above liquid in a closed vessel at a given temperature. The equilibrium vapour pressure is a sign of the evaporation rate of the liquid. The normal boiling point is the temperature at which the vapour pressure is the same as the atmospheric pressure.

Complete step by step answer:
We can consider a liquid inside a sealed beaker as an example of a dynamic system. In this, few molecules of the liquid are evaporated into vapour state, and few molecules are condensed into liquid state. The reaction rate of these two processes will be equal and the system is said to be dynamic equilibrium.
Since the molecules cannot escape from the container, the molecules of the vapour above the liquid surface would exert a pressure on the container walls. Therefore, we can define vapour pressure as the pressure exerted by a gaseous molecule above the liquid in a closed container.
Vapour pressure depends on factors such as the nature of liquid, temperature.
Nature of liquid: If molecules of liquid attach to each other strongly, molecules will have less tendency to liberate out as a gas, and will have lower vapour pressure.
Let us consider molecules of water and alcohols as an example. They form hydrogen bonds and have low vapour pressure. The molecules will have high vapour pressure, if there is weak interaction between them. When there is low interaction between molecules of liquids, they will have greater tendency to evaporate and hence, the vapour pressure will be high.
Stronger the interaction, lower will be the vapour pressure.
Weaker the interaction, higher will be the vapour pressure.
Temperature: At higher temperatures, several molecules would have required energy to escape from solid (or) liquid. At lower temperature, only a few molecules would have enough energy to escape from liquid (or) solid. As the temperature increases, there would be an increase in vapour pressure.
$\therefore $Option (A) and (B) are correct.

Note:
Surface area of solid (or) liquid in a gas does not affect the vapour pressure. The presence of dissolved substances in a liquid (or) solid also affects vapour pressure. Based on Raoult’s law, when a solute is added the vapour pressure of a pure solid (or) liquid is lowered. We know that Duhring’s rule defines that a linear relationship is seen between the temperatures at which two solutions exert equal vapour pressure.