Question

A closed vessel contains 8g of oxygen and 7g of nitrogen. The total pressure is 10 atm at a given temperature. If now oxygen is absorbed by introducing a suitable absorbent the pressure of the remaining gas in atm will be

• A. 2
• B. 10
• C. 4
• D. 5

Answer 1

Answer: (D)

5

Answer 2

From Dalton’s law final pressure of the mixture of nitrogen and oxygen

$P = P_{1} + P_{2} = \frac{\mu_{1}RT}{V} + \frac{\mu_{2}RT}{V} = \frac{m_{1}}{M_{1}}\frac{RT}{V} + \frac{m_{2}}{M_{2}}\frac{RT}{V} = \frac{8}{32}\frac{RT}{V} + \frac{7}{28}\frac{RT}{V} = \frac{RT}{2V}$ ⇒ $10 = \frac{RT}{2V}$ …..(i)

When oxygen is absorbed then for nitrogen let pressure is $P = \frac{7}{28}\frac{RT}{V}$ ⇒ $P = \frac{RT}{4V}$ …..(ii)

From equation (i) and (ii) we get pressure of the nitrogen $P = 5$atm.