The molar masses of four unknown gases are shown in the table. Molar Mass of Unknown Gases
Gas Molar Mass
A 44 g/mol
B 20 g/mol
C 30 g/mol
D 32 g/mol
Which gas is likely to have the lowest rate of diffusion?
a. Gas A
b. Gas B
c. Gas C
d. Gas D

a. Gas A has the lowest rate of diffusion

Given

The molar masses

Required

the lowest rate of diffusion

Solution

Graham's law: the rate of effusion of a gas is inversely proportional to the square root of its molar masses or  

the effusion rates of two gases = the square root of the inverse of their molar masses:  

So  :

The greater the molar mass, the smaller the rate

So gas A has the lowest rate

answer carbon and three oxygen atoms;