Which of the following statements is not correct ?

Options

A. Copper liberates hydrogen from acids.
B. In its higher oxidation states, manganese forms stable compounds with oxygen and fluorine
C. `Mn^(3+)` and `Co^(3+)` are oxidising agents in aqueous solution.
D. `Ti^(2+) and Cr^(2+)` are reducing agents in aqueous solution.

Explanation

To determine which statement is not correct among the options provided, we can analyze each statement based on the principles of electrochemistry and the electrochemical series.

### Step-by-Step Solution:

1. **Analyze Statement 1: "Copper liberates Hydrogen from Acids."**
- The electrochemical series ranks metals based on their ability to displace hydrogen from acids. Copper (Cu) has a reduction potential of +0.34 V for the reaction Cu²⁺ + 2e⁻ → Cu. The reduction potential for hydrogen ions (H⁺) is 0.0 V.
- Since copper has a higher reduction potential than hydrogen, it cannot displace hydrogen from acids. Therefore, this statement is **incorrect**.

2. **Analyze Statement 2: "In its higher oxidation state, manganese forms a stable compound with oxygen and fluorine."**
- Manganese can exist in various oxidation states, including +4, +6, and +7. Compounds like MnO₄⁻ (permanganate) and MnF₄ are stable. Thus, this statement is **correct**.

3. **Analyze Statement 3: "Mn³⁺ and MnO₄⁻ are oxidizing agents."**
- Mn³⁺ can act as an oxidizing agent because it can be reduced to Mn²⁺. Similarly, MnO₄⁻ is a strong oxidizing agent, capable of reducing to Mn²⁺ in acidic conditions. Therefore, this statement is **correct**.

4. **Analyze Statement 4: "Ti²⁺ and Cr²⁺ are reducing agents in aqueous solution."**
- Ti²⁺ can indeed act as a reducing agent, as it can be oxidized to Ti³⁺. Cr²⁺ can also act as a reducing agent, being oxidized to Cr³⁺. Thus, this statement is **correct**.

5. **Conclusion:**
- Based on the analysis, Statement 1 is the only incorrect statement, as copper does not liberate hydrogen from acids.

### Final Answer:
The statement that is not correct is **Statement 1: "Copper liberates Hydrogen from Acids."**