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Question

Which gas—nitrogen (N₂) or oxygen (O₂)— diffuses faster and at what relative rate? Both gases have the same temperature and pressure. Round the answer to three significant figures (rearrange the equation so that the larger molecular mass is in the numerator)

Answer 1

Look up and read about Graham's Law of Effusion:

rate gas 1 / rate gas 2 = sqrt MW gas 2 / sqrt MW gas 1

So, the rate of effusion/diffusion is inversely proportional to the square root of the molar mass.

For N₂ and O₂ we have the following:

molar mass N₂ = 28 g/mol

molar mass O₂ = 32 g/mol

So, N₂ will diffuse faster as it is the lighter gas (lower molar mass)

To find the relative rates, we use Graham's Law:

We will arbitrarily set the rate of of O₂ to 1.00 units. We then have...

rate N₂ / rate O₂ = sqrt 32 / sqrt 28

rate N₂ / 1.00 = 5.657 / 5.292

rate N₂ = 1.07 x faster than O₂