Question

Graham's law says that gas will effuse at a rate that is inversely proportional to the square root of its molecular mass, MM. Expressed mathematically:

rate1/rate2 = √MM2/MM1

solve:

1. Under the same conditions of temperature and pressure, how many times faster will hydrogen effuse compared to carbon dioxide? 
2. If the carbon dioxide in Problem 1 takes 32 seconds to effuse, how long will the hydrogen take?
3. what is the relative rate of diffusion of NH3 compared to He? Does NH3 effuse faster or slower than He?

Answer 1

Number one

Graham's Law of Diffusion/Effusion states that the rate of diffusion is inversely proportional to the square root of the molar mass.

 In equation form, rate gas 1/rate gas 2 = √MW gas 2/√MW gas 1

rate 1/rate 2 = √(44/2)g/mol

= 4.7 times faster

Number two

rate 1=(32/4.7)s

= 6.8 sec

Number three

r = √(4.0/17)g/mol

= 0.49

NH₃ effuses slower than HE