In which one of the following ways would the pH value of aqueous ammonia be effected by dissolving solid ammonium chloride in it ?

Options

A. Decreases
B. Increases
C. No effect
D. Impossible to predict

Answer

To solve the question regarding how the pH value of aqueous ammonia is affected by dissolving solid ammonium chloride in it, we can follow these steps:

### Step 1: Understand the Components
- Aqueous ammonia (NH₃) is a weak base and partially ionizes in water to form NH₄⁺ (ammonium ion) and OH⁻ (hydroxide ion).
- Ammonium chloride (NH₄Cl) is a salt that dissociates in water to give NH₄⁺ and Cl⁻ ions.

### Step 2: Analyze the Reaction
- When NH₄Cl is added to the solution of NH₃, it introduces more NH₄⁺ ions into the solution.
- The reaction can be represented as:
\[ NH₃ + H₂O \rightleftharpoons NH₄⁺ + OH⁻ \]

### Step 3: Effect of Adding NH₄Cl
- The addition of NH₄Cl increases the concentration of NH₄⁺ ions in the solution.
- According to Le Chatelier's principle, the equilibrium will shift to the left to counteract the increase in NH₄⁺ concentration, resulting in a decrease in the concentration of OH⁻ ions.

### Step 4: Determine the Change in pH
- As the concentration of OH⁻ decreases, the concentration of H⁺ ions (or H₃O⁺) will effectively increase, leading to a decrease in pH.
- Since pH is inversely related to the concentration of H⁺ ions, an increase in H⁺ concentration means a lower pH.

### Step 5: Conclusion
- Therefore, dissolving solid ammonium chloride in aqueous ammonia will decrease the pH of the solution.

### Final Answer
The pH value of aqueous ammonia will decrease upon dissolving solid ammonium chloride in it.

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