Question

The correct formula of the complex tetraammineaquachlorocobalt (III) chloride is

• A. \([\text{Cl(H}_2\text{O)(NH}_3)_4\text{Co}]\,\text{Cl}\)
• B. \([\text{CoCl(H}_2\text{O)(NH}_3)_4]\,\text{Cl}\)
• C. \([\text{Co(NH}_3)_4(\text{H}_2\text{O})\text{Cl}]\,\text{Cl}\)
• D. \([\text{CoCl(H}_2\text{O)(NH}_3)_4]\,\text{Cl}_2\)

Hint:

To write coordination compound formula: identify ligands in coordination sphere, calculate charge on complex ion using metal oxidation state, then add counter ions outside to make neutral compound.

Answer 1

The Correct Option is D

Step 1: Decode the name of the complex.
The complex is named: tetraammineaquachlorocobalt (III) chloride.
This means the coordination sphere contains:
- 4 ammine ligands \((NH_3)\)
- 1 aqua ligand \((H_2O)\)
- 1 chloro ligand \((Cl^-)\)
And central metal is cobalt in +3 oxidation state \((Co^{3+})\).
Step 2: Write the complex ion.
So coordination entity is:
\[ [\text{Co}(NH_3)_4(H_2O)Cl]^{x} \] Step 3: Determine charge on complex ion.
Oxidation state of Co = \(+3\).
Charge contributed by ligands:
- \(NH_3\) is neutral
- \(H_2O\) is neutral
- \(Cl^-\) contributes \(-1\)
So charge on complex:
\[ x = +3 + (-1) = +2 \] Thus the complex ion is:
\[ [\text{CoCl}(H_2O)(NH_3)_4]^{2+} \] Step 4: Add chloride ions outside to balance charge.
To balance \(2+\) charge, we need \(2\) chloride ions outside:
\[ [\text{CoCl}(H_2O)(NH_3)_4]\text{Cl}_2 \] Final Answer: \[ \boxed{[\text{CoCl}(H_2O)(NH_3)_4]\text{Cl}_2} \]