Assertion (A) Cu cannot liberate hydrogen from acids.
Reason (R ) Because it has positive electrode potential.

Options

A. Both assertion and reason are true, and reason is the correct explanation of the assertion.
B. Both assertion and reason are true but reason is not the correct explanation of assertion.
C. Assertion is not true but reason is true.
D. Both assertion and reason are false.

Explanation

To analyze the assertion and reason provided in the question, we will break down the concepts step by step.

### Step 1: Understanding the Assertion
The assertion states that "Cu cannot liberate hydrogen from acids." This means that when copper (Cu) is placed in an acidic solution, it does not produce hydrogen gas (H₂).

### Step 2: Understanding the Reason
The reason given is "Because it has a positive electrode potential." Electrode potential indicates the tendency of a substance to gain or lose electrons. A positive electrode potential means that the substance is less likely to lose electrons compared to hydrogen, which has a standard electrode potential of 0 V.

### Step 3: Electrochemical Series
In the electrochemical series, metals are arranged according to their standard electrode potentials. Metals with negative electrode potentials can displace hydrogen from acids, while those with positive electrode potentials cannot.

### Step 4: Position of Copper in the Electrochemical Series
Copper is located below hydrogen in the electrochemical series, which indicates that it has a positive electrode potential. This means that copper cannot displace hydrogen ions (H⁺) from the acid to form hydrogen gas.

### Step 5: Conclusion
Since copper has a positive electrode potential, it cannot liberate hydrogen from acids. Therefore, both the assertion and reason are correct, and the reason correctly explains the assertion.

### Final Answer
Both assertion (A) and reason (R) are true, and the reason is the correct explanation for the assertion.