By passage of 1 F of electricity, which is not obtained?

Options

A. 1 mol of Cu
B. `0.5` mol of Mg
C. 9 g of Al
D. `5.6` l of `O_(2)` gas at anode

Answer

To solve the problem of determining which substance is not obtained by the passage of 1 Faraday of electricity, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding 1 Faraday of Electricity**:
- 1 Faraday (F) of electricity corresponds to the charge of one mole of electrons, which is approximately 96500 coulombs.

2. **Analyzing Each Option**:
- **Option 1: 1 mole of Copper (Cu)**:
- Copper typically exists in the +2 oxidation state (Cu²⁺) and requires 2 electrons to be reduced to Cu.
- Therefore, to obtain 1 mole of Cu, we need 2 Faradays of electricity.
- Since we are only passing 1 Faraday, we can only obtain 0.5 moles of Cu.
- **Conclusion**: 1 mole of Cu cannot be obtained with 1 Faraday.

- **Option 2: 0.5 mole of Magnesium (Mg)**:
- Magnesium exists in the +2 oxidation state (Mg²⁺) and also requires 2 electrons to be reduced to Mg.
- Thus, 1 Faraday will yield 0.5 moles of Mg.
- **Conclusion**: 0.5 mole of Mg can be obtained with 1 Faraday.

- **Option 3: 9 grams of Aluminium (Al)**:
- Aluminium exists in the +3 oxidation state (Al³⁺) and requires 3 electrons to be reduced to Al.
- 1 mole of Al weighs 27 grams, so to obtain 9 grams (which is 1/3 of a mole), we need 1 Faraday (since 1 Faraday will yield 1/3 mole of Al).
- **Conclusion**: 9 grams of Al can be obtained with 1 Faraday.

- **Option 4: 5.6 liters of Oxygen gas (O₂)**:
- Oxygen is produced at the anode during the electrolysis of water. The reaction is:
\[ 2H_2O \rightarrow O_2 + 4H^+ + 4e^- \]
- This indicates that 4 Faradays are required to produce 22.4 liters of O₂ (at STP).
- Therefore, 1 Faraday will yield:
\[ \frac{22.4 \text{ L}}{4} = 5.6 \text{ L of O}_2 \]
- **Conclusion**: 5.6 liters of O₂ can be obtained with 1 Faraday.

3. **Final Conclusion**:
- The only option that cannot be obtained by the passage of 1 Faraday of electricity is **Option 1: 1 mole of Copper**.

### Answer:
**The substance that is not obtained by the passage of 1 Faraday of electricity is 1 mole of Copper.**

---