A: Electrode potential of hydrogen is pH dependet.
R: Electrode potential of hydrogen electrode is always zero.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements then mark (4)

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step 1: Analyze the Assertion (A)
The assertion states that "the electrode potential of hydrogen is pH dependent."

- The electrode potential of the hydrogen electrode (specifically the standard hydrogen electrode, SHE) is indeed dependent on the concentration of hydrogen ions (H⁺) in the solution.
- The relationship is given by the Nernst equation, which shows that the potential changes with the concentration of H⁺ ions.
- Since pH is defined as pH = -log[H⁺], a change in H⁺ concentration directly affects the pH, and thus, the electrode potential.

**Conclusion for A**: The assertion is **true**.

### Step 2: Analyze the Reason (R)
The reason states that "the electrode potential of hydrogen electrode is always zero."

- The standard hydrogen electrode (SHE) is defined to have a potential of 0 volts under standard conditions (1 M H⁺ concentration, 1 atm pressure of H₂, and at 25°C).
- However, this potential is only true under standard conditions. If the concentration of H⁺ ions changes (which affects the pH), the potential will also change and will no longer be zero.

**Conclusion for R**: The reason is **false** because the potential is not always zero; it only is under standard conditions.

### Final Conclusion
- Since the assertion (A) is true and the reason (R) is false, the correct answer is that A is true and R is false.