Question

Two perfumes are released at the same time. If one is standing 7.5 m from the point of release. Perfume A (molar mass 275 g/mol) and perfume B (molar mass 205 g/mol) at the same temperature. I. Which perfume will the person smell first and why?

Answer 1

According to Graham's Law of Diffusion," Diffusion of Gas is inversely proportional to square root of its Molecular Mass or Density".

                          rᵇ/rᵃ  =  $\sqrt{da/db}$
Or,
                          rᵇ/rᵃ  =  $\sqrt{Ma/Mb}$     ----- (1)
As, 
                          Ma  =  275 g/mol

                          Mb  =  205 g/mol

Putting Values in eq.1,

                          rᵇ/rᵃ  =  $\sqrt{275/205}$

                          rᵇ/rᵃ  =  1.15

Result:
          Perfume B will diffuse 1.15 times faster than Perfume A. Hence, Perfume B will be first smelled by the person.