For the oxidation of ferric oxalate to `CO_(2), 18F` of electricity is required. How many moles of ferric oxalate is oxidized ?

Explanation

To solve the problem of how many moles of ferric oxalate are oxidized when 18 Faraday of electricity is required, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chemical Formula of Ferric Oxalate**:
Ferric oxalate is represented as \( \text{Fe}_2(\text{C}_2\text{O}_4)_3 \). Each molecule contains 3 oxalate ions (\( \text{C}_2\text{O}_4^{2-} \)).

2. **Determine the Oxidation Reaction**:
The oxalate ion (\( \text{C}_2\text{O}_4^{2-} \)) is oxidized to carbon dioxide (\( \text{CO}_2 \)). The balanced half-reaction for the oxidation of one mole of oxalate ion is:
\[ \text{C}_2\text{O}_4^{2-} \rightarrow 2 \text{CO}_2 + 2 e^- \]
This indicates that 1 mole of oxalate produces 2 moles of electrons.

3. **Calculate the Total Moles of Electrons**:
Since 6 moles of electrons are produced from the oxidation of 3 moles of oxalate ions, we can establish that:
\[ 3 \text{ moles of } \text{C}_2\text{O}_4^{2-} \rightarrow 6 \text{ moles of } e^- \]

4. **Relate Faraday's Constant to Moles of Electrons**:
Faraday's constant (\( F \)) is approximately 96500 C/mol. Therefore, 1 Faraday corresponds to 1 mole of electrons. Thus, 18 Faraday corresponds to:
\[ 18 \text{ F} = 18 \text{ moles of electrons} \]

5. **Calculate the Moles of Oxalate Ion Oxidized**:
Since 6 moles of electrons correspond to 3 moles of oxalate, we can set up a proportion to find out how many moles of oxalate are oxidized with 18 moles of electrons:
\[ \frac{3 \text{ moles of } \text{C}_2\text{O}_4^{2-}}{6 \text{ moles of } e^-} = \frac{x \text{ moles of } \text{C}_2\text{O}_4^{2-}}{18 \text{ moles of } e^-} \]
Cross-multiplying gives:
\[ 6x = 54 \implies x = 9 \text{ moles of } \text{C}_2\text{O}_4^{2-} \]

6. **Convert Moles of Oxalate to Moles of Ferric Oxalate**:
Since each mole of ferric oxalate contains 3 moles of oxalate, we can find the moles of ferric oxalate:
\[ \text{Moles of ferric oxalate} = \frac{9 \text{ moles of } \text{C}_2\text{O}_4^{2-}}{3} = 3 \text{ moles of ferric oxalate} \]

### Final Answer:
Thus, the number of moles of ferric oxalate oxidized is **3 moles**.