A gas mixture is composed of 4.3 grams of hydrogen (density at STP = 0.089 g/L) and 2.9 grams of helium (density at STP = 0.179 g/L). What is the percentage (v/v) helium in the mixture?

If v/v = Volume of gas/total volume how would we find the volume of both of the gases?

Convert g H2 to volume using 1 mol H2 occupies 22.4 L at STP (alternatively you can use the PV = nRT and solve for volume). Convert g He to volume He the same way. Then plug into your v/v formula and solve for percent each.

To find the volume of each gas, we can use the formula:

Volume = Mass / Density

Let's calculate the volumes of hydrogen and helium:

For hydrogen:
Mass of hydrogen = 4.3 grams
Density of hydrogen at STP = 0.089 g/L

Volume of hydrogen = Mass of hydrogen / Density of hydrogen
Volume of hydrogen = 4.3 g / 0.089 g/L
Volume of hydrogen ≈ 48.31 L (rounded to two decimal places)

For helium:
Mass of helium = 2.9 grams
Density of helium at STP = 0.179 g/L

Volume of helium = Mass of helium / Density of helium
Volume of helium = 2.9 g / 0.179 g/L
Volume of helium ≈ 16.20 L (rounded to two decimal places)

Now that we have the volumes of both gases, we can find the total volume of the gas mixture by adding up the volumes of hydrogen and helium:

Total volume = Volume of hydrogen + Volume of helium
Total volume ≈ 48.31 L + 16.20 L
Total volume ≈ 64.51 L (rounded to two decimal places)

Now we can calculate the percentage (v/v) of helium in the mixture:

Percentage (v/v) helium = (Volume of helium / Total volume) x 100
Percentage (v/v) helium = (16.20 L / 64.51 L) x 100
Percentage (v/v) helium ≈ 25.10% (rounded to two decimal places)

Therefore, the gas mixture contains approximately 25.10% helium (v/v).