Question

Equal weights of methane and hydrogen are mixed in an empty container at ${25}^{o}C$. The fraction of the total pressure exerted by hydrogen is:

• A. $\frac{1}{2}$
• B. $\frac{8}{9}$
• C. $\frac{1}{9}$
• D. $\frac{16}{17}$

Answer 1

The correct option is B $\frac{8}{9}$

Let $xg$ each of hydrogen and methane are mixed.

The moles of hydrogen and methane are $\frac{x}{2}$ and $\frac{x}{16}$ respectively.

The mole fraction of hydrogen is $H_2=\frac{\frac{x}{2}}{\frac{x}{2}+\frac{x}{16}}=\frac{8}{9}$.

The partial pressure of hydrogen is the product of its mole fraction and total pressure.

Thus, $\frac{\text{Partial pressure of}{H}_2}{\text{Total pressure}}=\text{mole fraction of hydrogen}=\frac{8}{9}$.