Q78P - Chemistry: Molecular Nature Of Matter And Change

Question

When MCl₄(NH₃)₂ is dissolved in water and treated with AgNO₃, 2 mol of AgCl precipitates immediately for each mole of MCl₄(NH₃)₂. Give the coordination number of M in the complex.

Step-by-Step Solution

Answer

The coordination no. of the central metal ion is 4. 

Step 1: Concept used – Coordination

Coordination number is the number of ligands directly attached to a central metal ion in a coordination compound. These ligands can be ions, atoms, or molecules.

 

Step 2: Elucidation of coordination number

Because 2 mol of AgCl precipitates immediately for each mol of MCl₄(NH₃), while writing the actual formula of this coordination compound, we have to put 2Cl^- counter ions outside the brackets, which means they can easily dissolve in water:$\left({\text{MCl}}_2{\left({\text{NH}}_3\right)}_2\right){\text{Cl}}_2$

The most common coordination number is 6, but it is also not rare to see 2 and 4 as coordination numbers; so, the central metal ion in this compound has coordination number 4.