the correct statement with respect to the rate of electron transfer process is o-phen = o-phenanthroline ; *Co is labeled atom
(a)fast electron transfer; $\mathrm{L}=\mathrm{NH}_{3} ; \mathrm{n}=6$
(b)slow electron transfer ; $\mathrm{L}=\mathrm{o}$-phen; $\mathrm{n}=3$
(c)very slow electron transfer ; $\mathrm{L}=\mathrm{NH_3}$ ; $\mathrm{n}=3$
(d)very slow electron transfer: $\mathrm{L}=\mathrm{o}$-phen; $\mathrm{n}=3$
Answer
Answer: C ✓ checked by 4AB · confidence medium
Explanation
The [Co(NH₃)₆]²⁺/³⁺ self-exchange is one of the slowest known (k ≈ 10⁻⁶ M⁻¹ s⁻¹) because the spin change (high-spin d⁷ → low-spin d⁶) and the large Co–N bond-length change give a huge reorganisation energy; with o-phen the exchange is much faster. The option text should read n = 6 for NH₃.