Aqueous solution of potash alum is:

Options

A. alkaline
B. acidic
C. neutral
D. soapy

Explanation

To determine the nature of an aqueous solution of potash alum, we can follow these steps:

### Step 1: Identify the Composition of Potash Alum
Potash alum is chemically represented as K₂SO₄·Al₂(SO₄)₃·24H₂O. It consists of potassium sulfate (K₂SO₄) and aluminum sulfate (Al₂(SO₄)₃).

**Hint:** Remember that potash alum is a double salt containing both potassium and aluminum sulfates.

### Step 2: Understand the Nature of the Ions in Solution
When potash alum dissolves in water, it dissociates into its constituent ions: K⁺, SO₄²⁻, and Al³⁺. The potassium ion (K⁺) is derived from a strong base (KOH), while the aluminum ion (Al³⁺) can hydrolyze in water.

**Hint:** Identify which ions come from strong acids or bases and which ions may affect the pH of the solution.

### Step 3: Analyze the Hydrolysis of Aluminum Ions
Aluminum ions (Al³⁺) in solution can react with water to form aluminum hydroxide (Al(OH)₃) and release H⁺ ions, leading to an increase in acidity. This reaction can be represented as:
\[ \text{Al}^{3+} + 3 \text{H}_2\text{O} \rightleftharpoons \text{Al(OH)}_3 + 3 \text{H}^+ \]

**Hint:** Consider how the presence of Al³⁺ ions influences the concentration of H⁺ ions in the solution.

### Step 4: Determine the Overall pH of the Solution
Since the K⁺ ions come from a strong base and do not affect the pH significantly, and the Al³⁺ ions contribute to the formation of H⁺ ions, the overall solution will be acidic. The presence of H⁺ ions from the hydrolysis of Al³⁺ ions will lower the pH.

**Hint:** Recall that a solution is acidic if it has a higher concentration of H⁺ ions.

### Conclusion
Based on the analysis, the aqueous solution of potash alum is acidic due to the hydrolysis of aluminum ions, which leads to the release of H⁺ ions.

**Final Answer:** The aqueous solution of potash alum is **acidic**.