Question

What is the volume at 0 °C and 1 atm of a mixture that contains 4.0 g of methane and 2.0 g of helium?

Answer 1

The volume of the sample is 16.8 L.

1. Convert the mass of each gas to litres
2. Use the molar volume of each gas at STP to calculate its volume.
3. Add the two volumes.

Moles of CH₄ = 4.0 g CH₄ × `(1"mol CH₄")/(16.04" g CH₄")` = 0.25 mol CH₄

Moles of He = 2.0 g He × `(1" mol He")/(4.003" g He")` = 0.50 mol He

Volume of CH₄ = 0.25 mol CH₄ × `(22.414" L CH₄")/(1" mol CH₄")` = 5.6 L

Volume of He = 0.50 mol He × × `(22.414" L He")/(1" mol He")` = 11.2 L

Total volume = (5.6 + 11.2) L = 16.8 L