Question

Write the balance equation showing the oxidation of Fe²+ icons to Fe³+ ions by dichromate ions (Cr2O7²-).

Answer 1

To write the balanced equation for the oxidation of Fe²⁺ ions to Fe³⁺ ions by dichromate ions (Cr₂O₇²⁻), we first need to identify the half-reactions and then balance them. The dichromate ion is reduced in this reaction.

### Step 1: Write the half-reactions

1. **Oxidation half-reaction** (Fe²⁺ to Fe³⁺):
\[
\text{Fe}^{2+} \rightarrow \text{Fe}^{3+} + e^-
\]

2. **Reduction half-reaction** (Cr₂O₇²⁻ to Cr³⁺):
\[
\text{Cr}_2\text{O}_7^{2-} + 14 \text{H}^+ + 6 e^- \rightarrow 2 \text{Cr}^{3+} + 7 \text{H}_2\text{O}
\]

### Step 2: Balance the electrons

We need to balance the number of electrons transferred in both half-reactions. Since the oxidation half-reaction produces 1 electron and the reduction half-reaction consumes 6 electrons, we can multiply the oxidation half-reaction by 6:

\[
6 \text{Fe}^{2+} \rightarrow 6 \text{Fe}^{3+} + 6 e^-
\]

### Step 3: Combine the half-reactions

Now we can combine the balanced half-reactions:

\[
6 \text{Fe}^{2+} + \text{Cr}_2\text{O}_7^{2-} + 14 \text{H}^+ \rightarrow 6 \text{Fe}^{3+} + 2 \text{Cr}^{3+} + 7 \text{H}_2\text{O}
\]

### Final Balanced Equation

The final balanced equation for the oxidation of Fe²⁺ ions to Fe³⁺ ions by dichromate ions is:

\[
6 \text{Fe}^{2+} + \text{Cr}_2\text{O}_7^{2-} + 14 \text{H}^+ \rightarrow 6 \text{Fe}^{3+} + 2 \text{Cr}^{3+} + 7 \text{H}_2\text{O}
\]

This equation is now balanced in terms of mass and charge.