(i) `Cu+ 2HCl_(2) +H_(2)(g)` `[E_(Cu_(2+)//Cu^(@) = ).34V]`
(ii)`Zn + 2HClrightarrow ZNCl+ (2)+ H_(2) ((g))` `[E(ZN^(2+)//ZN^(@) = -0.76V]`
(iii) `Ag+ 2HCl rightarrow AgCl+(1)//(2) H_(2) (g)` `[E(Ag^(+)//Ag)^(@) =+0.80V]`
Which of the following reaction is feasible ?

Options

A. (ii)
B. (i)
C. (iii)
D. All of these

Explanation

To determine which of the given reactions is feasible, we will calculate the standard cell potential (E°cell) for each reaction and then use it to find the Gibbs free energy change (ΔG°). A reaction is feasible if ΔG° is negative, which occurs when E°cell is positive.

### Step-by-step Solution:

1. **Identify the Reactions and Their Standard Reduction Potentials**:
- (i) \( \text{Cu} + 2\text{HCl} \rightarrow \text{CuCl}_2 + \text{H}_2(g) \)
\( E°(\text{Cu}^{2+}/\text{Cu}) = +0.34 \, \text{V} \)
- (ii) \( \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2(g) \)
\( E°(\text{Zn}^{2+}/\text{Zn}) = -0.76 \, \text{V} \)
- (iii) \( \text{Ag} + 2\text{HCl} \rightarrow \text{AgCl} + \frac{1}{2} \text{H}_2(g) \)
\( E°(\text{Ag}^{+}/\text{Ag}) = +0.80 \, \text{V} \)

2. **Calculate E°cell for Each Reaction**:
- The standard reduction potential for hydrogen is \( E°(H^+/H_2) = 0.00 \, \text{V} \).

- **For Reaction (i)**:
\[ E°_{\text{cell}} = E°(H^+/H_2) - E°(\text{Cu}^{2+}/\text{Cu}) = 0.00 - 0.34 = -0.34 \, \text{V} \]

- **For Reaction (ii)**:
\[ E°_{\text{cell}} = E°(H^+/H_2) - E°(\text{Zn}^{2+}/\text{Zn}) = 0.00 - (-0.76) = 0.76 \, \text{V} \]

- **For Reaction (iii)**:
\[ E°_{\text{cell}} = E°(H^+/H_2) - E°(\text{Ag}^{+}/\text{Ag}) = 0.00 - 0.80 = -0.80 \, \text{V} \]

3. **Determine Feasibility Using ΔG°**:
- The relationship between Gibbs free energy and cell potential is given by:
\[ \Delta G° = -nFE°_{\text{cell}} \]
where \( n \) is the number of moles of electrons transferred, and \( F \) is Faraday's constant (approximately 96485 C/mol).

- **For Reaction (i)**:
\[ E°_{\text{cell}} = -0.34 \, \text{V} \quad \Rightarrow \quad \Delta G° > 0 \quad \text{(non-feasible)} \]

- **For Reaction (ii)**:
\[ E°_{\text{cell}} = +0.76 \, \text{V} \quad \Rightarrow \quad \Delta G° < 0 \quad \text{(feasible)} \]

- **For Reaction (iii)**:
\[ E°_{\text{cell}} = -0.80 \, \text{V} \quad \Rightarrow \quad \Delta G° > 0 \quad \text{(non-feasible)} \]

4. **Conclusion**:
- The only feasible reaction is Reaction (ii): \( \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2(g) \).

### Final Answer:
The feasible reaction is (ii) \( \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2(g) \).