How do you calculate molecular weight of a gas?

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Answer 1 · 2016-06-03T17:09:58

#MM=(mRT)/(PV)#

To find the molecular mass of a gas, we can assume it behaves ideally and use the ideal gas law:

#PV=nRT#

We can modify this law in terms of the molar mass (#MM#).

We know that the number of mole is equal to the mass (#m#) divided by th molecular mass (#MM#) of the gas:

#n=m/(MM)#

If we plug the expression of number of mole in the expression of the ideal gas law we get:

#PV=m/(MM)RT#

therefore, the molecular mass expression can be written as:

#MM=(mRT)/(PV)#

Thus, to find the molecular mass of a gas, we can measure its pressure, volume, mass and temperature.