MCQ Detailed View

[Pt(NH₃)₂]Cl₂ is a classic coordination compound, also called cisplatin in medicinal chemistry, but here we focus on its dissociation in water. In coordination compounds, the central metal ion is bonded to ligands forming a complex ion, and any counter ions are outside the coordination sphere.

In [Pt(NH₃)₂]Cl₂:

• 
  

  Pt²⁺ is the central metal ion.

  
  


• 
  

  NH₃ molecules are neutral ligands bonded directly to platinum and do not produce ions in solution.

  
  


• 
  

  Cl⁻ ions are counter ions outside the coordination sphere.

  
  

When [Pt(NH₃)₂]Cl₂ dissolves in water, it dissociates into:

1. 
   

   [Pt(NH₃)₂]²⁺ → one cation

   
   


2. 
   

   Cl⁻ → two separate chloride anions

   
   

Thus, the total number of ions produced = 1 + 2 = 3 ions.

This principle is important in inorganic chemistry, particularly for predicting electrolytic behavior and conductivity of coordination compounds. The neutral NH₃ ligands remain bound to the metal and do not contribute additional ions. Understanding this concept helps in analyzing solution properties, reaction mechanisms, and biological activity of metal complexes.

Other examples follow the same rule: only counter ions outside the coordination sphere dissociate in solution. For instance, [Co(NH₃)₆]Cl₃ produces 4 ions in solution: one [Co(NH₃)₆]³⁺ cation and three Cl⁻ anions.

Therefore, [Pt(NH₃)₂]Cl₂ produces 3 ions in solution, demonstrating the importance of recognizing ligands vs. counter ions in coordination chemistry.