When HCl gas is passed through a saturated solution of common salt, pure NaCl is precipitated because

Options

A. HCl is highly ionised in solution
B. HCl is highly soluble in water
C. The solubility product of NaCl is lowered by HCl
D. The ionic product of `[Na^(+) ] [ Cl^(-) ] ` exceeds the solubility product of NaCl

Answer

To solve the question regarding the precipitation of pure NaCl when HCl gas is passed through a saturated solution of common salt, we can follow these steps:

### Step 1: Understand the Components
When HCl gas is introduced to a saturated solution of NaCl (common salt), we have the following components in the solution:
- Sodium ions (Na⁺)
- Chloride ions (Cl⁻)
- Hydrogen ions (H⁺) from HCl

### Step 2: Recognize the Ionic Equilibrium
In a saturated solution of NaCl, the concentration of Na⁺ and Cl⁻ ions is at equilibrium, which means it is at its solubility product (Ksp). The solubility product is defined as:
\[ K_{sp} = [Na^+][Cl^-] \]

### Step 3: Effect of HCl on the Solution
When HCl is added to the solution, it dissociates into H⁺ and Cl⁻ ions. The addition of H⁺ ions does not affect the concentration of Na⁺ ions but increases the concentration of Cl⁻ ions.

### Step 4: Calculate the Ionic Product
The ionic product (IP) is defined as the product of the concentrations of the ions in the solution at any point, which can be expressed as:
\[ IP = [Na^+][Cl^-] \]
With the addition of HCl, the concentration of Cl⁻ increases, leading to an increase in the ionic product.

### Step 5: Compare Ionic Product and Solubility Product
For precipitation to occur, the ionic product must exceed the solubility product:
\[ IP > K_{sp} \]
Since the concentration of Cl⁻ has increased due to the addition of HCl, it is likely that:
\[ [Na^+][Cl^-] > K_{sp} \]
This condition leads to the precipitation of pure NaCl from the solution.

### Conclusion
The correct reason for the precipitation of pure NaCl when HCl gas is passed through a saturated solution of common salt is that the ionic product of Na⁺ and Cl⁻ exceeds the solubility product of NaCl.

### Final Answer
The correct statement is that the ionic product of sodium plus and chloride minus exceeds the solubility product of NaCl.

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