Question

In a gas mixture if molecular weights of all the species are equal than which one will be more, Mass average velocity or Molar average velocity?

(a) Mass average velocity

(b) Molar average velocity

(c) Both will have the same value

(d) Nothing definite can be said

This question was posed to me in a job interview.

My enquiry is from Concentration and Velocity topic in division Modes and Diffusion of Mass Transfer

Answer 1

The correct option is (c) Both will have the same value

Explanation: Average molar mass of the mixture=M(x1+x2+………+ xn)=M

                                                                                             (x1+x2+………+ xn=1)

                        Mass average velocity=Σuiρi/ρ=uiPui/P

                        Molar average velocity=Σciui/c=ρuiPi/P (P=cRT).