The diffusion coefficient of silver (Ag) in copper (Cu) has the following values:

T (K) D (m2s-1)
923 5.42 x 10-16
1173 1.34 x 10-13

(a) Calculate the activation energy for diffusion of silver in copper. Express your answer in units of J/mol.

(b) You have two specimens of copper, both of them polycrystalline. Specimen A has an average grain size of 3.091 μm, while Specimen B has an average grain size of 7.777 μm. Which specimen will silver diffuse through more quickly? Choose the best explanation.

I)Assuming both specimens are at the same temperature, the diffusivity should be the same through both samples as it is a materials property.

II)Specimen A should allow silver to diffuse more quickly due to its smaller grain size and increased grain boundary area.

III)Specimen A should allow silver to diffuse more quickly due to its smaller grain size and decreased grain boundary area.

IV)Specimen B should allow silver to diffuse more quickly due to its larger grain size and decreased grain boundary area.

V)Specimen B should allow silver to diffuse more quickly due to its larger grain size and increased grain boundary area.