Why pure NaCl is precipitated when HCl gas is passed in saturated solution of NaCl

Options

A. Impurities dissolves in HCl
B. The value of `[Na^(+)]` and `[Cl^(-)]` becomes smaller than `K_(sp)` of NaCl
C. The value of `[Na^(+)]` and `[Cl^(-)]` becomes greater than `K_(sp)` of NaCl
D. HCl dissolves in the water

Explanation

To understand why pure NaCl is precipitated when HCl gas is passed into a saturated solution of NaCl, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Saturated Solution**:
- A saturated solution of NaCl contains the maximum amount of NaCl that can dissolve in water at a given temperature. At this point, the solution is in equilibrium with solid NaCl.

2. **Dissociation of NaCl**:
- In a saturated NaCl solution, NaCl dissociates into its ions:
\[ \text{NaCl (s)} \rightleftharpoons \text{Na}^+ (aq) + \text{Cl}^- (aq) \]
- The concentrations of \(\text{Na}^+\) and \(\text{Cl}^-\) ions are at their maximum solubility limits.

3. **Effect of Adding HCl**:
- When HCl gas is passed into the solution, it dissolves to form hydrochloric acid, which dissociates into \(\text{H}^+\) and \(\text{Cl}^-\) ions:
\[ \text{HCl (g)} \rightarrow \text{H}^+ (aq) + \text{Cl}^- (aq) \]
- This increases the concentration of \(\text{Cl}^-\) ions in the solution.

4. **Le Chatelier's Principle**:
- According to Le Chatelier's principle, if the concentration of one of the products in a saturated solution increases, the equilibrium will shift to the left to counteract this change.
- In this case, the increase in \(\text{Cl}^-\) ions causes the equilibrium to shift towards the formation of solid NaCl.

5. **Precipitation of NaCl**:
- As a result of the shift in equilibrium, solid NaCl begins to precipitate out of the solution:
\[ \text{Na}^+ (aq) + \text{Cl}^- (aq) \rightarrow \text{NaCl (s)} \]
- This leads to the formation of pure NaCl as a precipitate.

6. **Conclusion**:
- Therefore, when HCl gas is passed into a saturated NaCl solution, the increased concentration of \(\text{Cl}^-\) ions causes the precipitation of pure NaCl.