The reaction :
`Zn(s) + 2AgCl(g) rightarrow ZnCl_(2)(aq) + 2Ag(s)`
occurs in the cell `Zn|ZnCl_(2)` (1M solution), AgCl(s) | Ag. The number of Faradays required from the external source for this reaction to occur in the cell is:

Options

A. 2
B. 3
C. 1
D. zero

Explanation

To determine the number of Faradays required for the reaction:

\[ \text{Zn}(s) + 2\text{AgCl}(s) \rightarrow \text{ZnCl}_2(aq) + 2\text{Ag}(s) \]

we need to analyze the oxidation and reduction processes occurring in the cell.

### Step 1: Identify the oxidation and reduction half-reactions

1. **Oxidation half-reaction**: Zinc (Zn) is oxidized to zinc ions (Zn²⁺).
\[ \text{Zn}(s) \rightarrow \text{Zn}^{2+}(aq) + 2e^- \]

2. **Reduction half-reaction**: Silver ions (Ag⁺) are reduced to silver metal (Ag).
\[ 2\text{Ag}^+(aq) + 2e^- \rightarrow 2\text{Ag}(s) \]

### Step 2: Balance the overall reaction

From the half-reactions, we can see that:
- 1 mole of Zn releases 2 moles of electrons.
- 2 moles of Ag⁺ consume 2 moles of electrons.

This means that the electrons lost by zinc are exactly equal to the electrons gained by silver ions. Therefore, the overall reaction is balanced.

### Step 3: Calculate the total number of moles of electrons transferred

In this reaction, a total of 2 moles of electrons are transferred (as indicated by the 2e⁻ in the oxidation half-reaction).

### Step 4: Determine the number of Faradays required

1 Faraday (F) is the charge of 1 mole of electrons, which is approximately 96485 coulombs. Since we have 2 moles of electrons transferred, the number of Faradays required is:

\[ \text{Number of Faradays} = \text{moles of electrons} = 2 \text{ F} \]

### Final Answer

The number of Faradays required from the external source for this reaction to occur in the cell is **2 Faradays**.

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