Question

In water saturated air, the mole fraction of water vapour is $0.02$. If the total pressure of the saturated air is $1.2\, atm$, the partial pressure of dry air is :

• A. 1.18 atm
• B. 1.76 atm
• C. 1.176 atm
• D. 0.98 atm

Answer 1

Answer: (C)

1.176 atm

Answer 2

$X_{H_2O} = 0.02$
$\therefore X_{gas} = 0.98$
$P_{total} =1.2 \,atm$
partial pressure of dry-air $= P_T \times$ mole fraction of dry-air
Partial pressure of dry-air $= 1.2\, atm \times 0.98$
$= 1 .176 \,atm$.