Which of the following statement is NOT correct?

(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 oxidizing agents in aqueous solution.

(D) \(Ti^{2+}\) and \(Cr^{2+}\) are reducing agents in an aqueous solution.

Choose the correct answer from the options given below:

(A) Only

The correct answer is option 3. (A) Only.

The statement that is NOT correct is: (A) Copper liberates hydrogen from acids.

Statement (3) which says "Copper liberates hydrogen from acids" is not entirely accurate. Here's a more nuanced explanation:

Copper (Cu): As a noble metal, copper is less reactive than many other metals.

Reaction with dilute acids: At room temperature, copper generally doesn't react with dilute acids like hydrochloric acid \((HCl)\) or sulfuric acid \((H_2SO_4)\). These dilute acids lack the oxidizing power necessary to overcome copper's low reactivity.

However, there are some exceptions:

Concentrated acids: Concentrated sulfuric acid \((H_2SO_4)\) can react with copper at high temperatures, producing sulfur dioxide \((SO_2)\) and hydrogen sulfide \((H_2S)\) gases, not pure hydrogen \((H_2)\).

Oxidizing acids: Copper can react with strong oxidizing acids like concentrated nitric acid (HNO3) to liberate hydrogen gas. In this case, the concentrated HNO3 acts as an oxidizing agent, readily oxidizing copper and releasing hydrogen gas.

Therefore, statement (3) is an oversimplification. While copper doesn't readily react with dilute acids to produce hydrogen, it can react with some concentrated or oxidizing acids under specific conditions.

Here's why the other statements are correct:

(B) Manganese forms stable compounds with oxygen and fluorine in its higher oxidation states. This is true. Manganese (Mn) can exhibit oxidation states from +2 to +7. In higher oxidation states (+4, +6, and +7), manganese readily forms stable oxides and fluorides.

(C) \(Mn^{3+}\) and \(Co^{3+}\) are oxidizing agents in aqueous solution. This is also true. Metal ions in higher oxidation states tend to be oxidizing agents as they can gain electrons and reduce their oxidation state. Mn³⁺ and Co³⁺ can accept electrons from other species, oxidizing them in the process.

(D) \(Ti^{2+}\) and \(Cr^{2+}\) are reducing agents in an aqueous solution. This is correct. Metal ions in lower oxidation states tend to be reducing agents as they can lose electrons and increase their oxidation state. Ti²⁺ and Cr²⁺ can donate electrons to other species, reducing them in the process.

Copper (Cu) is a noble metal and doesn't readily react with dilute acids at room temperature. Therefore, statement (A) is incorrect.

So the answer is (3) (A) Only.