Question

The activation energy of nickel atoms in FCC iron is 280 kJ/mol and carbon atoms in FCC iron is 142 kJ/mol. (a) What does this tell you about the comparative diffusion of nickel and carbon in iron? (b) Can you explain why the activation energies are so drastically different? (c) Find a way to qualitatively explain how much energy is 142 kJ to a non-scientist.

Also, is the non-steady diffusion process more sensitive to temperature or time? Explain using appropriate equations.

Answer 1

Diffusion is basically the movement of atoms in any material. It increases as the temperature or thermal energy possessed by the atoms increases. The diffusion rate is related to temperature or thermal energy by the Arrhenius equation:

Rate = Ae^-Ea/RT

where A is a constant, R is gas constant (8.314 J.mol-1.K-1), T is the absolute temperature (K), and E_a is the activation energy (J.mol-1).

(a) The higher activation energy of Ni atoms tells about the higher thermal energy possessed by Nickel particles compared to carbon atoms.