Question

Given that vapour pressure of water vapour at ${29}^{\circ }C$ is $30torr$ and relative humidity is 0.9. Calculate the partial pressure of water vapour at the same temperature

• A. $9torr$
• B. $30torr$
• C. $87torr$
• D. $27torr$

Answer 1

The correct option is D $27torr$

Relative humidity is defined as :
$\text{R.H}=\frac{\text{Partial pressure of water vapour}}{\text{Vapour pressure of water at the same temperature}}$

For R.H to be 0.9 :
$0.9=\frac{\text{Partial pressure}}{30}\text{Partial pressure}=27torr$