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 among the given options is not correct, we will analyze each option one by one.

### Step 1: Analyze Option A
**Statement A:** Copper liberates hydrogen from acids.

- **Analysis:** In the electrochemical series, copper is positioned below hydrogen. Metals that are below hydrogen in this series cannot displace hydrogen from acids. Therefore, copper cannot liberate hydrogen gas from acids.

**Conclusion:** This statement is incorrect.

### Step 2: Analyze Option B
**Statement B:** In its higher oxidation states, manganese forms stable compounds with oxygen and fluorine.

- **Analysis:** Manganese can exhibit a +7 oxidation state (as in KMnO4) and forms stable compounds with both oxygen and fluorine in this state. Thus, this statement is correct.

**Conclusion:** This statement is correct.

### Step 3: Analyze Option C
**Statement C:** Mn³⁺ and Co³⁺ are oxidizing agents in aqueous solution.

- **Analysis:** Both Mn³⁺ and Co³⁺ can act as oxidizing agents because they can accept electrons and thus oxidize other substances. Therefore, this statement is correct.

**Conclusion:** This statement is correct.

### Step 4: Analyze Option D
**Statement D:** Ti²⁺ and Cr²⁺ are reducing agents in aqueous solution.

- **Analysis:** Ti²⁺ and Cr²⁺ can indeed act as reducing agents in aqueous solutions, as they can donate electrons to other species, thereby reducing them. Thus, this statement is correct.

**Conclusion:** This statement is correct.

### Final Conclusion
After analyzing all the statements, we find that:

- **Option A** is the only incorrect statement.

Therefore, the answer is **A**.

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