Which of the following statements is `//` are correct ?

Options

A. The electrolysis of concentrated `H_(2)SO_(4)` at `0-5^(@)C` using a `Pt ` electrode produces `H_(2)S_(2)O_(8)`.
B. The electrolysis of a brine solution produces `NaClO_(3)` and `NaClO`.
C. The electrolysis of `CuSO_(4)` solution using `Pt` electrodes causes the liberation of `O_(2)` at anode and the deposition of copper at cathode.
D. All electrolytic reactions are redox reactions.

Explanation

To determine which statements are correct regarding electrolysis, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement 1: The electrolysis of concentrated H2SO4 at 0-5 degrees Celsius using a platinum electrode produces H2S2O8.**
- **Analysis**: During the electrolysis of concentrated sulfuric acid (H2SO4), oxidation occurs at the anode, leading to the formation of peroxydisulfuric acid (H2S2O8). The reaction involves the oxidation of sulfate ions and the liberation of hydrogen ions and electrons.
- **Conclusion**: This statement is **correct**.

2. **Statement 2: The electrolysis of a brine solution produces NaClO3 and NaCl.**
- **Analysis**: A brine solution is a mixture of sodium chloride (NaCl) and water. During electrolysis, at the cathode, hydrogen ions are reduced to form hydrogen gas, while at the anode, chloride ions are oxidized to form chlorine gas. The formation of NaClO3 does not occur in this process.
- **Conclusion**: This statement is **incorrect**.

3. **Statement 3: The electrolysis of copper sulfate using a platinum electrode causes liberation of O2 at the anode and deposition of copper at the cathode.**
- **Analysis**: In the electrolysis of copper sulfate (CuSO4), copper ions (Cu²⁺) are reduced at the cathode to deposit copper metal. At the anode, hydroxide ions (OH⁻) are oxidized to produce oxygen gas (O2) and water. This confirms the liberation of O2 at the anode and deposition of copper at the cathode.
- **Conclusion**: This statement is **correct**.

4. **Statement 4: All electrolytic reactions are redox reactions.**
- **Analysis**: Electrolytic reactions involve the transfer of electrons, where oxidation occurs at the anode and reduction occurs at the cathode. This simultaneous occurrence of oxidation and reduction classifies all electrolytic reactions as redox reactions.
- **Conclusion**: This statement is **correct**.

### Final Conclusion:
- **Correct Statements**: 1, 3, and 4.
- **Incorrect Statement**: 2.