Question

The values of dissociation constant of [Cu(NH₃)₄]²⁺ and [Co(NH₃)₆]³⁺ are 1.0 × 10⁻¹² and 6.2 × 10⁻³⁴ respectively. Which complex would be more stable and why?

Answer 1

1. The stability of a coordination complex is inversely related to its dissociation constant (K_n).
2. A lower dissociation constant indicates that the complex is less likely to break apart in solution, meaning it is more stable.
3. For the complexes [Cu(NH₃)₄]²⁺ and [Co(NH₃)₆]³⁺, the dissociation constants are 1.0 × 10⁻¹² and 6.2 × 10⁻³⁴ respectively.
4. Since [Co(NH₃)₆]³⁺ has a much smaller dissociation constant, it is far more stable than [Cu(NH₃)₄]²⁺.
5. This greater stability is due to the higher positive charge on the cobalt ion (Co³⁺), which attracts ligands more strongly and forms more stable coordinate bonds with ammonia.

Therefore, [Co(NH₃)₆]³⁺ is the more stable complex.