Compute diffusion coefficients for the interdiffusion of carbon in both (a) α-iron (BCC) and (b) γ-iron (FCC) at 1000˚C. Assume that D0 for the interdiffusion of carbon in α-iron and in γ-iron are 1.1 × 10-6 and 2.3 × 10-5 m2/s, respectively, and that Qd are 80 and 148 kJ/mol, respectively.

Explanation:

According to Ficks first law, the relation between diffusion flux and diffusion coefficient is as follows.

             J =

where, D = function of temperature

         D =

where,   = pre-exponential independent of temperature

(a)  Substituting the given values into the above formula, we will calculate the value of D as follows.

                   D =

                      =

                      =

                      =

                     =

Therefore, diffusion coefficient for the inter-diffusion of carbon in -iron is .

(b)   For -iron we will calculate the value of D as follows.

                D =

                      =  

                      =

                      =

                      =

Therefore, diffusion coefficient for the inter-diffusion of carbon in -iron is .

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

b. th3 n4zc4 pl4t3 15 c0nv3rg1ng w1th the s0uth 4m3ric4n pl4t3.