Question

Knowing that the value of K for [Cu(NH₃)₄]²⁺ is 4.5 × 10¹¹ and for [Cu(CN)₄]²⁻ is 2.0 × 10²⁷, suggest which complex species will furnish less Cu²⁺ ions in solution.

Answer 1

The stability constant (K) represents the equilibrium constant for the complex’s formation from its metal ions and ligands. A higher K value indicates a more stable complex, which means it is less likely to dissociate and release free Cu²⁺ ions into the solution.

For [Cu(NH₃)₄]²⁺, the stability constant K = 4.5×10¹¹

For [Cu(CN)₄]²⁻, the stability constant K = 2.0 × 10²⁷

Since [Cu(CN)₄]²⁻ has a significantly higher K value, it is much more stable compared to [Cu(NH₃)₄]²⁺. This means [Cu(CN)₄]²⁻ will furnish fewer Cu²⁺ions in solution because it is less likely to dissociate and release Cu²⁺ ions.