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)

From Dalton's law, final pressure of the mixture of nitrogen and oxygen
$p_{\text{mix}}=p_1+p_2$
$=\frac{{\mu }_{1}RT}{V}+\frac{{\mu }_{2}RT}{V}$
$=\frac{m_1}{M_1}\frac{RT}{V}+\frac{m_2}{M_2}\frac{RT}{V}$
$=\frac{8}{32}\frac{RT}{V}+\frac{7}{28}\frac{RT}{V}=\frac{RT}{2V}$
$10=\frac{RT}{2V}...(i)$
When oxygen is absorbed then for nitrogen by pressure
$p=\frac{7}{28}\frac{RT}{V}$
$p=\frac{RT}{4V}...(ii)$
From Eqs. (i) and (ii), we get
Pressure of the nitrogen
$p=5atm$