Question

Write half reaction equations and overall balanced redox reaction equations for the following,
a) 2Al +3l2 produce 2All3
b) 2FeCl2 + Cl2 produce 2FeCl3

Answer 1

To write the half-reaction equations and the overall balanced redox reactions for the given equations, let's start with each reaction separately.

### a) \( 2 \text{Al} + 3 \text{I}_2 \rightarrow 2 \text{AlI}_3 \)

**Step 1: Identify the oxidation and reduction half-reactions.**
- Aluminum (Al) is oxidized from 0 to +3.
- Iodine (I₂) is reduced from 0 to -1.

**Oxidation Half-Reaction:**
\[
2 \text{Al} \rightarrow 2 \text{Al}^{3+} + 6 \text{e}^-
\]

**Reduction Half-Reaction:**
\[
3 \text{I}_2 + 6 \text{e}^- \rightarrow 6 \text{I}^-
\]

**Step 2: Balancing the half-reactions together.**
Combining the two half-reactions gives:
\[
2 \text{Al} + 3 \text{I}_2 \rightarrow 2 \text{Al}^{3+} + 6 \text{I}^-
\]
After including the AlI₃ formation:
\[
2 \text{Al} + 3 \text{I}_2 \rightarrow 2 \text{AlI}_3
\]

So the balanced redox reaction is:
\[
\text{Overall Reaction: } 2 \text{Al} + 3 \text{I}_2 \rightarrow 2 \text{AlI}_3
\]

### b) \( 2 \text{FeCl}_2 + \text{Cl}_2 \rightarrow 2 \text{FeCl}_3 \)

**Step 1: Identify the oxidation and reduction half-reactions.**
- Iron (Fe) in FeCl₂ is oxidized from +2 to +3.
- Chlorine (Cl₂) is reduced from 0 to -1.

**Oxidation Half-Reaction:**
\[
2 \text{Fe}^{2+} \rightarrow 2 \text{Fe}^{3+} + 2 \text{e}^-
\]

**Reduction Half-Reaction:**
\[
\text{Cl}_2 + 2 \text{e}^- \rightarrow 2 \text{Cl}^-
\]

**Step 2: Balancing the half-reactions together.**
Combining the two half-reactions gives:
\[
2 \text{Fe}^{2+} + \text{Cl}_2 \rightarrow 2 \text{Fe}^{3+} + 2 \text{Cl}^-
\]
After forming FeCl₃, we can express the balanced equation:
\[
2 \text{FeCl}_2 + \text{Cl}_2 \rightarrow 2 \text{FeCl}_3
\]

So the balanced redox reaction is:
\[
\text{Overall Reaction: } 2 \text{FeCl}_2 + \text{Cl}_2 \rightarrow 2 \text{FeCl}_3
\]

### Summary
- For \( 2 \text{Al} + 3 \text{I}_2 \rightarrow 2 \text{AlI}_3 \):
- Oxidation: \( 2 \text{Al} \rightarrow 2 \text{Al}^{3+} + 6 \text{e}^- \)
- Reduction: \( 3 \text{I}_2 + 6 \text{e}^- \rightarrow 6 \text{I}^- \)
- Overall: \( 2 \text{Al} + 3 \text{I}_2 \rightarrow 2 \text{AlI}_3 \)

- For \( 2 \text{FeCl}_2 + \text{Cl}_2 \rightarrow 2 \text{FeCl}_3 \):
- Oxidation: \( 2 \text{Fe}^{2+} \rightarrow 2 \text{Fe}^{3+} + 2 \text{e}^- \)
- Reduction: \( \text{Cl}_2 + 2 \text{e}^- \rightarrow 2 \text{Cl}^- \)
- Overall: \( 2 \text{FeCl}_2 + \text{Cl}_2 \rightarrow 2 \text{FeCl}_3 \)