Which of the following statements is/are correct ?

Options

A. The stability constant of `[Co(NH_(3))_(6)]^(3+)` is greater than that of `[Co(NH_(3))_(6)]^(2+)`
B. Among `F^(-), Cl^(-), Br^(-)" and "I^(-),F^(-)` forms more stable complexes due to small size.
C. `[Cu(NH_(3))_(4)]^(2+)` is thermodynamically more stable than `[Zn(NH_(3))_(4)]^(2+)`
D. Among `[Fe(CN)_(6)]^(3-), [Fe(H_(2)O)_(6)]^(2+)" and "[Fe(en)_(3)]^(3+),[Fe(CN)_(6)]^(3-)` is most stable.

Answer

A, C

Explanation

(c ) According to Irving Williams order, stability of +2 oxidation state for 3d transition series follows :
`Mn^(II) lt Fe^(II) lt Co^(II) lt Ni^(II) lt Cu^(II) gt Zn^(II)`
(d) `[Fe("en")_(3)]^(3+)` is more stable due to chelation.