Question

Choose the correct statement(s):
Given that vapour pressure of water vapour at ${29}^{\circ }C$ is $30torr$.
(where R.H is relative humidity)

• A. For R.H to be 0.5 , partial pressure of water vapour should be $60torr$ at the same temperature
• B. For R.H to be 0.66 , partial pressure of water vapour should be $20torr$ at the same temperature
• C. For R.H to be 0.33 , partial pressure of water vapour should be $90torr$ at the same temperature
• D. For R.H to be 0.9 , partial pressure of water vapour should be $27torr$ at the same temperature

Answer 1

Answer: (B), (D)

For R.H to be 0.9 , partial pressure of water vapour should be $27torr$ at the same temperature

Relative humidity is defined as :
$\text{R.H}=\frac{\text{Partial pressure of water vapour}}{\text{Vapour pressure of water at the same temperature}}$
Case (a) :
For R.H to be 0.5 :
$0.5=\frac{\text{Partial pressure}}{30}\text{Partial pressure}=15torr$

Case (b) :
For R.H to be 0.66 :
$0.66=\frac{\text{Partial pressure}}{30}\text{Partial pressure}=20torr$

Case (c) :
For R.H to be 0.33 :
$0.33=\frac{\text{Partial pressure}}{30}\text{Partial pressure}=10torr$

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