COMEDK2023ChemistryCoordination Compounds
Aqueous CuSO ₄ changes its colour from sky blue to deep blue on addition of NH ₃ because
Options
- ACu ²⁺ forms hydrate
- BCu ²⁺ changes to Cu ⁺
- C[ Cu ( H ₂ O )₄ ]²⁺ is labile complex and changes to [ Cu ( NH ₃ )₄ ]²⁺ as NH ₃ is stronger ligand than H ₂ O
- DCu ⁺ changes to Cu ²⁺
Correct answer
C. [ Cu ( H ₂ O )₄ ]²⁺ is labile complex and changes to [ Cu ( NH ₃ )₄ ]²⁺ as NH ₃ is stronger ligand than H ₂ O
Step-by-step solution
As, H ₂ O is a weak field ligand and thus [ Cu ( H ₂ O )₄ ]²⁺ absorbs red light in visible spectrum. But the colour appears blue because [ Cu ( H ₂ O )₄ ]²⁺ is a labile complex and changes to [ Cu ( NH ₃ )₄ ]²⁺ , where NH ₃ is strong field ligand thus absorbs yellow light of visible spectrum and impart blue colour.