Question

Which factors do not affect the vapour pressure of a liquid at equilibrium?
a.Intermolecular forces of attraction
b.The volume of liquid present
c.The temperature of liquid.
A.Only a
B.Only b
C.a and b
D.b and c

Answer 1

Hint: Change in temperature changes the average kinetic energy of the molecules. Higher the kinetic energy, lower is the intermolecular forces. Intermolecular forces of attraction are the bonding in between two molecules.

Complete step by step answer:
Vapour pressure is the pressure exerted by the vapours on the surface of liquid in equilibrium with its liquid state.
The vapour pressure of a liquid is independent of the volume. Let us assume that we have decreased the volume of the container in which vapour pressure was exerted by the liquid then some vapours condenses back to the liquid to maintain the same vapour pressure. If the volume is increased then some liquids evaporate to form the vapour.
When the temperature is increased the kinetic energy of molecules increases and hence more vapour will evaporate than before. With increase in temperature the intermolecular forces of attraction decrease. So the vapour pressure will increase with increases in temperature.Intermolecular forces of attraction are those forces which hold to or more atoms or molecules. If the intermolecular forces of attraction are high then it will be difficult to evaporate the liquid from its surface as compared to the molecules that have low intermolecular forces of attraction which will easily evaporate

Hence, the change in volume will not affect the vapour pressure, so the correct option is B.

Note:
The other factors that affect vapour pressure are humidity and surface area. Vapour pressure is independent of surface area and humidity. We consider the vapour pressure at a certain constant level of humidity in air. When all other factors are kept constant then we can study the impact of humidity on vapour pressure.