Question

A mixture of carbon monoxide and carbon dioxide is found to have a density of 1.7 g/lit at S.T.P. The mole fraction of carbon monoxide is:

• A. 0.37
• B. 0.4
• C. 0.3
• D. 0.5

Answer 1

Answer: (A)

0.37

The molecular weight of the mixture $\left(M_{mix}\right)$ is calculated by using the ideal gas equation.

At STP,

$T=273K$

$P=1atm$

$M_{mix}=\frac{dRT}{P_{mix}}$.

Substitute values in the above expression:

$M_{mix}=\frac{1.7\times 0.0821\times 273}{1}=1.7\times 22.4gms$

The molecular weight of the mixture $\left(M_{mix}\right)$ can also be calculated by using the expression,

$M_{mix}=X_{CO}\times M_{CO}+(1-X_{CO}).M_{C{O}_2}$

Here, $X_{CO}$ and $M_{CO}$ represents the mole fraction and molecular weight of CO and $(1-X_{CO})$ and $M_{C{O}_2}$ represents the mole fraction and molecular weight of $C{O}_2$.

Thus $1.7\times 22.4=X_{CO}\times 28+(1-X_{CO})\times 44$

$X_{CO}=0.37$

The mole fraction of carbon monoxide is $0.37$.