During the electrolysis of aqueous zinc nitrate.

Options

A. Zinc plates out at the cathode
B. Zinc plates out at the anode
C. Hydrogen gas,`H_(2)` , is evolved at the cathode
D. Oxygen gas,`O_(2)` , is evolved at the anode

Explanation

### Step-by-Step Solution:

1. **Identify the Electrolyte**: The electrolyte in this case is aqueous zinc nitrate, which can be represented as Zn(NO₃)₂. In solution, it dissociates into zinc ions (Zn²⁺) and nitrate ions (NO₃⁻).

2. **Determine the Ions Present**: In addition to zinc and nitrate ions, water (H₂O) is also present in the solution. However, water does not dissociate significantly into H⁺ and OH⁻ ions.

3. **Identify the Electrodes**: During electrolysis, we have two electrodes: the cathode (where reduction occurs) and the anode (where oxidation occurs).

4. **Reduction at the Cathode**: At the cathode, we need to determine which species will undergo reduction. The two possible candidates are Zn²⁺ and H₂O. We compare their reduction potentials:
- The reduction potential for Zn²⁺ + 2e⁻ → Zn is higher than that for the reduction of water (which would produce hydrogen gas).
- Therefore, Zn²⁺ will gain electrons and be reduced to solid zinc (Zn).

**Reaction at Cathode**:
\[ \text{Zn}^{2+} + 2e^- \rightarrow \text{Zn (s)} \]

5. **Oxidation at the Anode**: At the anode, we consider the oxidation of the nitrate ion (NO₃⁻) and water (H₂O). The oxidation potential of water is higher than that of nitrate ions, and since nitrogen in nitrate is already at its maximum oxidation state (+5), it cannot be oxidized further.

**Reaction at Anode**:
\[ 2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^- \]

6. **Analyze the Options**:
- **Option 1**: Zinc plates out at the cathode. **True** (solid zinc is deposited).
- **Option 2**: Zinc plates out at the anode. **False** (oxidation occurs at the anode, not deposition).
- **Option 3**: Hydrogen gas (H₂) is evolved at the cathode. **False** (no gas is evolved at the cathode).
- **Option 4**: Oxygen gas (O₂) is evolved at the anode. **True** (oxygen is produced at the anode).

7. **Conclusion**: The correct options are 1 and 4.

### Final Answer:
The correct statements during the electrolysis of aqueous zinc nitrate are:
1. Zinc plates out at the cathode.
4. Oxygen gas is evolved at the anode.