Choose the most stable complex ion on the ground of values of instability constants:

Answer options

1. [Ag(NH3)2] + Kн = 5, 89 · 10−8
2. [Fe(CN)6] 3− Kн = 1 · 10−31
3. [Ag(CN)2] − Kн = 1 · 10−21
4. [Ni(CN)4] 2− Kн = 1 · 10−22
5. [Co(NH3)6] 2+ Kн = 4, 07 · 10−5