A helium/oxygen (heliox) mixture of 80%/20% has a density compared with oxygen of:

Question

Quizplus · Accepted Answer

The density of a gas mixture is determined by the mass of each gas and their respective molar masses. Helium has a molar mass of 4 g/mol and oxygen has a molar mass of 32 g/mol. Therefore, an 80%/20% heliox mixture has a molar mass of (0.8*4 g/mol) + (0.2*32 g/mol) = 6.4 g/mol. This is lower than the molar mass of oxygen alone (32 g/mol), which means the density of heliox compared to oxygen is lower. The ratio of the densities can be calculated as (32 g/mol)/(6.4 g/mol) = 5, so the density of heliox compared to oxygen is 5 times lower, or 1.8 times lower.

A Helium/oxygen (Heliox) Mixture of 80%/20% Has a Density Compared