How do you calculate molecular weight of a gas?

1 Answer
Jun 3, 2016

Answer:

#MM=(mRT)/(PV)#

Explanation:

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.