Assertion : Copper dissolves in dilute nitric acid but not in dilute HCI.
Reason : Copper has positive `E^@`.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true and reason not is the correct explanation of assertion.
C. If assertion is trun but reason is false.
D. If both assertion and reason are false.

Answer

To solve the given question, we will analyze both the assertion and the reason step by step.

### Step 1: Understand the Assertion
The assertion states that "Copper dissolves in dilute nitric acid but not in dilute HCl."

- **Explanation**: Copper (Cu) can react with dilute nitric acid (HNO3) because nitric acid acts as an oxidizing agent. When copper is placed in dilute nitric acid, it undergoes oxidation, leading to the formation of copper nitrate (Cu(NO3)2) and nitrogen oxides (NO or NO2) as byproducts.

### Step 2: Understand the Reason
The reason given is "Copper has a positive E° value."

- **Explanation**: The standard electrode potential (E°) indicates the tendency of a species to gain electrons (be reduced). A positive E° value means that the species is more likely to be oxidized. In the case of copper, it has a positive E° value, which means it can easily lose electrons and thus can be oxidized in the presence of a suitable oxidizing agent like nitric acid.

### Step 3: Analyze the Reaction with HCl
The assertion also states that copper does not dissolve in dilute HCl.

- **Explanation**: Hydrochloric acid (HCl) is not an oxidizing agent; it is a strong acid that does not provide the necessary conditions for copper to be oxidized. Therefore, copper remains unreacted when placed in dilute HCl.

### Step 4: Conclusion
Since both the assertion and the reason are true, and the reason correctly explains why copper dissolves in dilute nitric acid but not in dilute HCl, we conclude that:

- **Final Answer**: Both assertion and reason are true, and the reason is the correct explanation of the assertion. Therefore, the answer is option A.

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