Chemical reactions involve interation of atoms and molecules. A large number of atoms `//` molecules `(` approximately `6.023xx10^(23))` are present in a few grams of any chemical compound varying with their atomic `//` molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry, biochemistry, electrochemistry, and radiochemistry. The following example illustrates a typical case, involving chemical `//` electrochemical reaction, which requires a clear understanding of the mole concept.
A `4.0M` aqueous solution of `NaCl` is prepared and `500mL` of this solution is electrolyzed. This leads to the evolution of chlorine gas at one of the electrodes `(` atomic mass of `Na ` is 23 and `Hg` is `200)(1F=96500C)`.
The total number of moles of chlorine gas evolved is

Options

A. `0.5`
B. `1.0`
C. `2.0`
D. `3.0`

Explanation

To solve the problem step by step, we need to determine the total number of moles of chlorine gas (Cl₂) evolved when 500 mL of a 4.0 M NaCl solution is electrolyzed.

### Step 1: Calculate the number of moles of NaCl in the solution.
The formula to calculate the number of moles (n) is given by:
\[ n = \text{Molarity} \times \text{Volume (in liters)} \]

Given:
- Molarity (M) = 4.0 M
- Volume (V) = 500 mL = 0.5 L

Substituting the values:
\[ n = 4.0 \, \text{mol/L} \times 0.5 \, \text{L} = 2.0 \, \text{moles of NaCl} \]

### Step 2: Determine the moles of Cl⁻ ions available.
In NaCl, each formula unit provides one Cl⁻ ion. Therefore, the number of moles of Cl⁻ ions is equal to the number of moles of NaCl:
\[ \text{Moles of Cl}^- = 2.0 \, \text{moles} \]

### Step 3: Calculate the moles of Cl₂ gas produced.
The electrolysis of Cl⁻ ions at the anode produces Cl₂ gas according to the half-reaction:
\[ 2 \text{Cl}^- \rightarrow \text{Cl}_2 + 2 \text{e}^- \]

From the reaction, we can see that 2 moles of Cl⁻ produce 1 mole of Cl₂. Therefore, the moles of Cl₂ produced can be calculated as follows:
\[ \text{Moles of Cl}_2 = \frac{\text{Moles of Cl}^-}{2} = \frac{2.0}{2} = 1.0 \, \text{mole of Cl}_2 \]

### Final Answer:
The total number of moles of chlorine gas (Cl₂) evolved is **1.0 mole**.

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