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Gas calculations

How would I work this out:
Calculate the relative molecular mass of a gas which has a density of 2.165dm-3 at 298k and 101kpa.
Original post by Sarwat.
How would I work this out:
Calculate the relative molecular mass of a gas which has a density of 2.165dm-3 at 298k and 101kpa.

Hello!
It asks for relative molecular mass so assume ideal behavior and just use PM=dRT
where P=pressure, M=molecular mass, d=density, R=ideal gas constant, T=absolute temperature

It can be derived from the ideal gas equation easily,
PV=nRT
PV=(m/M)RT
PM=(m/V)RT
m/V = density so
PM=dRT

And make sure to substitute everything in coherent SI units and the final answer is also in SI units (kg mol-1)


hope this helps
It comes handy if you can memorize equations like this
for quicker calculations...

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