Q33 / 150 · MHT CET 2026 (16 April Shift 1) · Chemistry
Identify oxidation state of cobalt ion in the complex, $[\text{Co(NH}_3)_5\text{Br}]\text{SO}_4$ .
- A$+2$
- Correct answerB$+3$
- C$+1$
- D$+4$
Solution
Let the oxidation state of cobalt be $x$.
The given coordination compound dissociates into a complex cation $[\text{Co(NH}_3)_5\text{Br}]^{2+}$ and a sulfate anion $\text{SO}_4^{2-}$.
The overall charge on the complex cation is $+2$.
Ammonia ($\text{NH}_3$) is a neutral ligand with an oxidation state of $0$, and bromide ($\text{Br}^-$) has an oxidation state of $-1$.
Summing the oxidation states of the central metal atom and the ligands:
$x + 5(0) + (-1) = +2$
$x - 1 = +2$
$x = +3$
The oxidation state of cobalt in the complex is $+3$.
Answer: $+3$
The given coordination compound dissociates into a complex cation $[\text{Co(NH}_3)_5\text{Br}]^{2+}$ and a sulfate anion $\text{SO}_4^{2-}$.
The overall charge on the complex cation is $+2$.
Ammonia ($\text{NH}_3$) is a neutral ligand with an oxidation state of $0$, and bromide ($\text{Br}^-$) has an oxidation state of $-1$.
Summing the oxidation states of the central metal atom and the ligands:
$x + 5(0) + (-1) = +2$
$x - 1 = +2$
$x = +3$
The oxidation state of cobalt in the complex is $+3$.
Answer: $+3$
Hence, the correct answer is option: 'B'.