Question

A gas mixture is made by combining 5.1 g each of Ar, Ne, and an unknown diatomic gas. At STP, the mixture occupies a volume of 11.53 L. What is the molar mass of the unknown gas?

Answer 1

total mole of gas -

at STP 1 mole of gas occupy volume 22.414 L then 11.53 liter gas = 11.53 / 22.414 = 0.51441 mole

mole of gas = mass of gas / molar mass of gas

no. of mole of Ar = 5.1 / 39.948 = 0.127666 mole

no.of mole of Ne = 5.1 / 20.1797 = 0.2527 mole

no. of mole of unknown gas = (total mole of gas) - ( mole of Ar + mole of Ne)

no. of mole of unknown gas = ( 0.51441 ) - ( 0.127666 + 0.2527) = 0.134 mole

0.134 mole of unknown gas = 5.1 gm of gas then 1 mole of unknown gas = 5.1 / 0.134 = 38.0597 gm

molar mass of unknown gas = 38.0597 gm / mol