Question

The oxidation number of Co in complex [Co(H$_2$NCH$_2$CHNH$_2$)$_3$]$_2$(SO$_4$)$_3$ is:

• A. 2
• B. 3
• C. 5
• D. 4

Answer 1

The Correct Option is B

To determine the oxidation number of cobalt (Co) in the complex [Co(H₂NCH₂CHNH₂)₃]₂(SO₄)₃, we follow these steps: 

• The complex formula [Co(H₂NCH₂CHNH₂)₃]₂(SO₄)₃ includes:
  • Cobalt [Co]
  • Tris(ethylenediamine) ligands [H₂NCH₂CHNH₂]
  • Sulfate ions (SO₄)
• Ethylenediamine (en) is a neutral ligand, so it does not affect the overall charge of the complex.
• Sulfate ion (SO₄) has a charge of -2. Since there are three sulfate ions, their total contribution to the charge is 3 × (-2) = -6.
• The complex as a whole is neutral, so the sum of charges within [Co(en)₃]₂ must be +6 to balance the -6 from the sulfates.
• Let x be the oxidation state of one cobalt ion. Therefore, the equation considering 2 Co centers is:
  \(x(2) + 0 = +6\)
• Solve for x:
  \(2x = 6\)
  \(x = 3\)
• Thus, the oxidation number of Co in the complex is \(+3\).

Answer 2

To determine the oxidation number of Co in the complex [Co(H₂NCH₂CH₂NH₂)₃]₂(SO₄)₃, we need to analyze the complex and its components.

1. Identify the ligands:

The ligand is H₂NCH₂CH₂NH₂, which is ethylenediamine (en). Ethylenediamine is a neutral ligand, meaning it has no charge.

2. Determine the counter ions:

The counter ion is SO₄^2- (sulfate). There are 3 sulfate ions, so the total negative charge is 3 × (-2) = -6.

3. Calculate the charge of the complex ion:

Since the overall compound is neutral, the total positive charge of the complex ion must balance the total negative charge of the sulfate ions. Therefore, the total positive charge of the 2 complex ions is +6. So each [Co(en)₃] complex has a +3 charge.

4. Set up the equation and solve for the oxidation number of Co:

Let x be the oxidation number of Co.

The complex ion is [Co(en)₃]³⁺.

The equation is:

x + 3(0) = +3

x = +3

Therefore, the oxidation number of Co in the complex is +3.

The correct answer is: Option A: 3