Question

Write half equation reaction and overall balance redox reaction equations for the following.
A. 2Al (s) + 3l2 (s) = 2All3 (s)
B. 2FeCl2 (aq) +Cl2 (g) = 2FeCl3 (aq)

Answer 1

To write the half-reaction equations and the overall balanced redox reaction equations for the given reactions, we first need to identify the oxidation and reduction processes involved.

### A. Reaction: \( 2 \text{Al} (s) + 3 \text{I}_2 (s) \rightarrow 2 \text{AlI}_3 (s) \)

**Step 1: Identify oxidation and reduction**
- Aluminum (Al) is oxidized from 0 to +3.
- Iodine (I\(_2\)) is reduced from 0 to -1.

**Step 2: Write half-reactions**

**Oxidation half-reaction:**
\[
2 \text{Al} (s) \rightarrow 2 \text{Al}^{3+} + 6 e^{-}
\]

**Reduction half-reaction:**
\[
3 \text{I}_2 (s) + 6 e^{-} \rightarrow 6 \text{I}^- (s)
\]

**Step 3: Combine the half-reactions**
The overall balanced redox reaction is already given as:
\[
2 \text{Al} (s) + 3 \text{I}_2 (s) \rightarrow 2 \text{AlI}_3 (s)
\]

### B. Reaction: \( 2 \text{FeCl}_2 (aq) + \text{Cl}_2 (g) \rightarrow 2 \text{FeCl}_3 (aq) \)

**Step 1: Identify oxidation and reduction**
- Iron (Fe) in FeCl\(_2\) is oxidized from +2 to +3.
- Chlorine (Cl\(_2\)) is reduced from 0 to -1.

**Step 2: Write half-reactions**

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

**Reduction half-reaction:**
\[
\text{Cl}_2 (g) + 2 e^{-} \rightarrow 2 \text{Cl}^- (aq)
\]

**Step 3: Combine the half-reactions**
When combining, we must ensure that the electrons lost in the oxidation half-reaction match the electrons gained in the reduction half-reaction:
\[
2 \text{Fe}^{2+} + \text{Cl}_2 + 2 e^{-} \rightarrow 2 \text{Fe}^{3+} + 2 \text{Cl}^-
\]

**Overall balanced redox reaction is:**
\[
2 \text{FeCl}_2 (aq) + \text{Cl}_2 (g) \rightarrow 2 \text{FeCl}_3 (aq)
\]

### Summary of Half-Reactions
- **For Reaction A:**
- Oxidation: \( 2 \text{Al} (s) \rightarrow 2 \text{Al}^{3+} + 6 e^{-} \)
- Reduction: \( 3 \text{I}_2 (s) + 6 e^{-} \rightarrow 6 \text{I}^- (s) \)

- **For Reaction B:**
- Oxidation: \( 2 \text{Fe}^{2+} \rightarrow 2 \text{Fe}^{3+} + 2 e^{-} \)
- Reduction: \( \text{Cl}_2 (g) + 2 e^{-} \rightarrow 2 \text{Cl}^- (aq) \)

Both reactions are balanced and confirm the changes in oxidation states for the respective elements involved.