Problem: Gas Y effuses half as fast as O2. What is the molar mass of gas Y?

FREE Expert Solution

We’re being asked to calculate molar mass of gas Y if it effuses half as fast as O2.


Recall that Graham's Law of Effusion allows us to compare the rate of effusion of two gases. Graham's Law states that the rate of effusion of a gas is inversely proportional to its molar mass.


rate=1MMgas


This means that when comparing two gases:


rategas 1rategas 2=MMgas 2MMgas 1


Let's designate O2 as gas 2 and the gas Y as gas 1


rate gas Y = 0.5 (rate O2)

  • rategas 1rategas 2=0.5


The molar mass of O2 is:

O2       2 O × 16 g/mol O = 32 g/mol     

                               Sum = 32 g/mol


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Problem Details

Gas Y effuses half as fast as O2. What is the molar mass of gas Y?