The graph shows plots of kobs versus [X-] for the anations [Co(en)2(NO2)(DMSO)]2+ + X- [...

The graph shows plots of kobs versus [X-] for the anations [Co(en)₂(NO₂)(DMSO)]²⁺ + X^- [Co(en)₂(NO₂)X]⁺ + DMSO . The rate for DMSO exchange was determined . (Graph created using data from W. R. Muir, C. H. Langford, Inorg. Chem. , 1968 , 7 , 1032.)

All three reactions are presumed to have the same mechanism.

a. Why is the DMSO exchange so much faster than the other reactions?

b. Why are the curves shaped as they are?

c. Explain what the limiting rate constants (at high concentration) are in terms of the rate laws for D and I_d mechanisms.

d. The limiting rate constants are and and NO₂ ^- respectively. For SCN^-, the limiting rate constant can be estimated as . Do these values constitute evidence for an I_d mechanism?