A gas mixture contains 25 % He and 75 % CH4 by volume at a given temperature and pressure. The percentage by mass of methane in the mixture is approximately

Question

A gas mixture contains 25 % He and 75 % CH4 by volume at a given temperature and pressure. The percentage by mass of methane in the mixture is approximately (A) 75% (B) 25% (C) 92% (D) 8%

Tardigrade Admin · Accepted Answer

Since temperature and pressure are constant, we can assume it to be in STP condition.

Now, let the total volume be

100 L

Moles of

He

present

= \frac{25}{22.4} = 1.12 m o l

Mass of

He

present

= 1.12 \times 4 = 4.48 g

Moles of

C H_{4}

present

= \frac{75}{22.4} = 3.35 m o l

Mass of

C H_{4}

present

= 3.35 \times 16 = 53.60 g

Hence, the mass percentage of

C H_{4} = \frac{53.60}{58.08} \times 100 = 92.28%

Q. A gas mixture contains 25%He and 75%CH4​ by volume at a given temperature and pressure. The percentage by mass of methane in the mixture is approximately____

75%

25%

92%

8%

Q. A gas mixture contains $25% He$ and $75% C H_{4}$ by volume at a given temperature and pressure. The percentage by mass of methane in the mixture is approximately____