If a gas effuses #1.89# times as fast as #"COCl"_2(g)#, what is its molar mass?
2 Answers
Graham's law states that :
For 2 gases this becomes:
So:
So:
The compound that effuses faster must have lighter molecules, if they are both at the same temperature.
Take the ratio that is
Square that value,
This is the mass ratio between heavier and lighter molecules, because these have the same mean kinetic energies and root mean squared speeds, as consequence of the equipartition of energy :
So the lighter molecules have mass
where 98.9 = C + O + 2Cl = 12.01 + 16.00 + 35.45ยท2 = 98.9.