Q57 / 180 · NEET 2026 (Re-NEET) · Chemistry
The formula of tetraammineaquachloridocobalt(III) chloride is
- Correct answerA$[\text{Co(NH}_3)_4(\text{H}_2\text{O})\text{Cl}]\text{Cl}_2$
- B$[\text{Co(NH}_3)_4\text{Cl}_2]\times\text{H}_2\text{O}$
- C$[\text{Co(NH}_3)_4]\text{Cl}_3\times\text{H}_2\text{O}$
- D$[\text{Co(NH}_3)_4(\text{H}_2\text{O})\text{Cl}]\text{Cl}$
Solution
The complex name is tetraammineaquachloridocobalt(III) chloride.
The central metal ion is cobalt(III), which means $\text{Co}$ is in the $+3$ oxidation state.
The ligands inside the coordination sphere are four ammine ($\text{NH}_3$) molecules which are neutral, one aqua ($\text{H}_2\text{O}$) molecule which is neutral, and one chlorido ($\text{Cl}^-$) ion which has a $-1$ charge.
The coordination sphere is $[\text{Co}(\text{NH}_3)_4(\text{H}_2\text{O})\text{Cl}]$.
The charge on the complex ion is calculated as $+3 + 4(0) + 0 + (-1) = +2$.
To balance the $+2$ charge of the complex ion, two chloride ($\text{Cl}^-$) counter ions are required outside the coordination sphere.
Thus, the formula of the complex is $[\text{Co}(\text{NH}_3)_4(\text{H}_2\text{O})\text{Cl}]\text{Cl}_2$.
Answer: $[\text{Co(NH}_3)_4(\text{H}_2\text{O})\text{Cl}]\text{Cl}_2$
The central metal ion is cobalt(III), which means $\text{Co}$ is in the $+3$ oxidation state.
The ligands inside the coordination sphere are four ammine ($\text{NH}_3$) molecules which are neutral, one aqua ($\text{H}_2\text{O}$) molecule which is neutral, and one chlorido ($\text{Cl}^-$) ion which has a $-1$ charge.
The coordination sphere is $[\text{Co}(\text{NH}_3)_4(\text{H}_2\text{O})\text{Cl}]$.
The charge on the complex ion is calculated as $+3 + 4(0) + 0 + (-1) = +2$.
To balance the $+2$ charge of the complex ion, two chloride ($\text{Cl}^-$) counter ions are required outside the coordination sphere.
Thus, the formula of the complex is $[\text{Co}(\text{NH}_3)_4(\text{H}_2\text{O})\text{Cl}]\text{Cl}_2$.
Answer: $[\text{Co(NH}_3)_4(\text{H}_2\text{O})\text{Cl}]\text{Cl}_2$
Hence, the correct answer is option: 'A'.