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
[NEET-2019 (Odishall​

Answer 1

Given:

Mole fraction of water vapour, y2 = 0.02

Total pressure of saturated air, P = 1.2 atm

To Find:

Partial pressure of dry air

Calculation:

- Mole fraction of dry air = 1 - mole fraction of water vapour

⇒ y1 = 1 - y2

⇒ y1 = 1 - 0.02

⇒ y1 = 0.98

- Partial pressure of dry air = Mole fraction of dry air × Total pressure

⇒ P1 = y1 × P

⇒ P1 = 0.98 × 1.2

⇒ P1 = 1.176 atm

- So the partial pressure of dry air is 1.176 atm