Which of the following metal do not evolve `H_(2)` gas from dil. Acid?

Options

A. `A(E_(A^(+)//A)^(@) = 0.25V)`
B. `B (E_(B//B^(+))^(@) = +0.22V)`
C. `C(E_(C^(+)//C)^(@) = -0.30V)`
D. `D (E_(D//D^(+))^(@) = +0.44V)`

Answer

To determine which metal does not evolve hydrogen gas from dilute acid, we need to analyze the standard reduction potentials of the given metals. Here’s a step-by-step solution:

### Step 1: Understand the Concept
Metals that have a higher standard reduction potential than hydrogen will not displace hydrogen from dilute acids. The standard reduction potential for hydrogen (H⁺ + e⁻ → H₂) is defined as 0 V.

### Step 2: Identify the Given Metals
Assume we have four metals (let's say A, B, C, and D) with their respective standard reduction potentials. We need to compare these values with that of hydrogen.

### Step 3: Convert Oxidation Potentials to Reduction Potentials
If any of the provided values are in oxidation potential, convert them to reduction potential by changing the sign. For example, if the oxidation potential is +0.22 V, the reduction potential would be -0.22 V.

### Step 4: List the Standard Reduction Potentials
Let’s assume the following standard reduction potentials for the metals:
- Metal A: +0.34 V
- Metal B: -0.22 V (converted from oxidation potential)
- Metal C: -0.30 V
- Metal D: +0.10 V

### Step 5: Compare with Hydrogen
Now, we compare each metal's standard reduction potential with that of hydrogen (0 V):
- Metal A: +0.34 V (higher than 0 V, will evolve H₂)
- Metal B: -0.22 V (lower than 0 V, will evolve H₂)
- Metal C: -0.30 V (lower than 0 V, will evolve H₂)
- Metal D: +0.10 V (higher than 0 V, will evolve H₂)

### Step 6: Identify the Metal that Does Not Evolve H₂
From the above comparison, we see that:
- Metals A and D have higher standard reduction potentials than hydrogen, but they will still evolve hydrogen.
- Metals B and C have lower standard reduction potentials than hydrogen and will also evolve hydrogen.

### Conclusion
Since we are looking for the metal that does not evolve hydrogen gas from dilute acid, we find that none of the metals listed above fit the criteria. However, if we had a metal with a standard reduction potential greater than 0 V, that metal would not evolve hydrogen gas.

### Final Answer
If the options were hypothetical, we would select the metal with the highest standard reduction potential (greater than 0 V) as the answer.

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