Question

What is the unit of diffusion coefficient?

(a) mol m^-2 s^-1

(b) mol m^-3

(c) m^2 s^-1

(d) KJ mol^-1

The question was posed to me by my school teacher while I was bunking the class.

I would like to ask this question from Fick’s Law, Carbon Steels in section Diffusion in Solids & Ferrous Materials of Engineering Material & Metallurgy

Answer 1

Correct choice is (c) m^2 s^-1

To explain I would say: The unit of the diffusion coefficient (D) is mole per square meter per second (m^2 s^-1). The units of flux (J), concentration (c), and enthalpy are mol  m^2 s^-1, mol m^-3, and KJ mol^-1 in that order.