Question

Which of the following equation correctly depicts the relation between the vapor pressure of a liquid and it’s temperature?

(a) Vapor pressure increases linearly with the increase in temperature of the liquid

(b) Vapor pressure increases slightly with the increase in temperature of the liquid at low temperatures and the rate of increase goes high at higher temperatures

(c) Vapor pressure increases rapidly with the increase in temperature of the liquid at low temperatures and the rate of increase goes low at higher temperatures

(d) Vapor pressure remains unchanged with the increase in temperature of the liquid

I have been asked this question during an interview for a job.

My question is from Vapor Pressure in portion Properties of Fluids of Fluid Mechanics

Answer 1

The correct answer is (b) Vapor pressure increases slightly with the increase in temperature of the liquid at low temperatures and the rate of increase goes high at higher temperatures

The explanation is: Vapor pressure is closely related to molecular activity which is in turn dependant on the temperature of the liquid. With the increase in temperature molecular activity of a vapor increases slowly at first and then rapidly. Similar is the nature of variaion of vapor pressure.