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 problem, we need to analyze the two statements provided in the question:

**Assertion (A):** The electrode potential of hydrogen is pH dependent.
**Reason (R):** The electrode potential of the hydrogen electrode is always zero.

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states that the electrode potential of hydrogen is pH dependent. This can be understood through the Nernst equation, which relates the electrode potential to the concentration of ions involved in the reaction.
- For the hydrogen electrode, the half-reaction can be written as:
\[ \text{H}^+ + e^- \leftrightarrow \frac{1}{2} \text{H}_2 \]

2. **Applying the Nernst Equation:**
- The Nernst equation is given by:
\[ E = E^0 - \frac{RT}{nF} \ln Q \]
where \( Q \) is the reaction quotient.
- For the hydrogen electrode, at standard conditions, the standard electrode potential \( E^0 \) is defined as 0 V.

3. **Calculating the Effect of pH:**
- The concentration of hydrogen ions (\( \text{H}^+ \)) is related to pH by the equation:
\[ \text{pH} = -\log[\text{H}^+] \]
- Therefore, we can express the Nernst equation in terms of pH:
\[ E = 0 - \frac{0.0591}{n} \log[\text{H}^+] \]
- Substituting \( [\text{H}^+] = 10^{-\text{pH}} \):
\[ E = -0.0591 \cdot \text{pH} \]
- This shows that the electrode potential is indeed dependent on pH.

4. **Understanding the Reason:**
- The reason states that the electrode potential of the hydrogen electrode is always zero. This statement is misleading.
- While the standard electrode potential is defined as 0 V for comparison purposes, the actual potential can vary based on the concentration of hydrogen ions in the solution (which is affected by pH).

5. **Conclusion:**
- The assertion is true because the electrode potential of hydrogen does depend on pH.
- The reason is false because the electrode potential is not always zero; it can vary based on the conditions of the solution.

### Final Answer:
- Assertion (A) is true.
- Reason (R) is false.
- Therefore, the correct answer is: Assertion is true, Reason is false.