Question

A gas mixture is made by combining 8.7 g each of Ar, Ne, and an unknown diatomic gas. At STP, the mixture occupies a volume of 17.28 L. What is the molar mass of the unknown gas

Answer 1

Answer: Molar mass of the unknown gas is 73.153 g/mol.

Step-by-step explanation:

Given: Mass of each gas = 8.7 g

Volume = 17.28 L

Let us assume that the molar mass of gas is m g/mol.

Molar mass of Ar is 40 g/mol and Ne is 20 g/mol.

Hence, total moles of each gas are as follows.

`((8.7)/(40) + (8.7)/(20) + (8.7)/(m)) mol`

At STP, the total volume of these gases is as follows.

`((8.7)/(40) + (8.7)/(20) + (8.7)/(m)) mol * 22.4 L = 17.28 L\\((8.7)/(40) + (8.7)/(20))22.4 L + (8.7)/(m) * 22.4 L = 17.28 L\\14.616 + (8.7)/(m) * 22.4 L = 17.28 L\\(8.7)/(m) * 22.4 L = (17.28 L - 14.616)\\(8.7)/(m) * 22.4 L = 2.664 \\m = 73.153 g/mol`

Thus, we can conclude that molar mass of the unknown gas is 73.153 g/mol.