Question

What is the relative humidity of a gas with a partial pressure of water vapor is 5 mm Hg and vapor pressure 8 mm Hg?

(a) 25%

(b) 32.5%

(c) 45%

(d) 62.5%

This question was addressed to me during an interview.

This intriguing question originated from Partial Saturation Terminology in chapter Two Phase Gas – Liquid Systems, Phase Rule and Vapor-Liquid Equilibria of Basic Chemical Engineering

Answer 1

Right option is (d) 62.5%

To explain I would say: Relative humidity = 5/8*100 = 62.5%.