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 (H₂) from dilute acid, we need to analyze the standard reduction potentials (SRP) of the metals in question. The key concept is that metals with a more negative SRP can reduce hydrogen ions (H⁺) to hydrogen gas, while metals with a more positive SRP cannot.

### Step-by-Step Solution:

1. **Understand Standard Reduction Potential (SRP)**:
- The SRP indicates how easily a metal can be reduced. A more negative SRP means the metal is a better reducing agent and can displace hydrogen from acids.

2. **Identify the Metals**:
- List the metals provided in the question. For this example, let's assume we are considering metals like Zinc (Zn), Copper (Cu), and Iron (Fe).

3. **Check the SRP Values**:
- Look up the SRP values for each metal:
- Zinc (Zn): SRP = -0.76 V
- Copper (Cu): SRP = +0.34 V
- Iron (Fe): SRP = -0.44 V

4. **Compare SRP Values with Hydrogen**:
- The SRP for hydrogen ions (H⁺) is 0 V.
- Metals with SRP values less than 0 V can reduce H⁺ to H₂, while those with SRP values greater than 0 V cannot.

5. **Determine Which Metal Cannot Evolve H₂**:
- Zinc (SRP = -0.76 V): Can evolve H₂.
- Copper (SRP = +0.34 V): Cannot evolve H₂.
- Iron (SRP = -0.44 V): Can evolve H₂.

6. **Conclusion**:
- The metal that does not evolve hydrogen gas from dilute acid is **Copper (Cu)**.