Question

Find out the oxidation number of Copper (Cu) in the following coordination compound: [Cu(NH$_3$)$_4$]SO$_4$.

Hint:

Neutral ligands like NH$_3$, H$_2$O, CO do not affect oxidation number; only counter ions (like SO$_4^{2-}$, Cl$^-$) matter.

Answer 1

Step 1: Identify ligands and counter ions.
The given compound is \([Cu(NH_3)_4]SO_4\). - The coordination sphere is \([Cu(NH_3)_4]^{2+}\). - Sulphate ion \((SO_4^{2-})\) is outside the coordination sphere. Step 2: Charge balance.
Let oxidation state of Cu = \(x\).
Ammonia \((NH_3)\) is a neutral ligand, so its charge = 0. \[ x + (4 \times 0) = +2 \] \[ x = +2 \] Conclusion:
The oxidation number of copper in the compound \([Cu(NH_3)_4]SO_4\) is: \[ \boxed{+2} \]