Which of the following is not true about potash alum

Options

A. its empirical formula is `KAI(SO_(4))_(2).12H_(2)O`
B. IT aqueus solution is basic
C. It is used in dyeing industries
D. On heating it melts in its water of crystallization

Answer

To determine which statement about potash alum is not true, we will analyze each option provided in the question step by step.

### Step 1: Identify the empirical formula of potash alum.
- Potash alum is commonly represented by the empirical formula KAl(SO₄)₂·12H₂O.
- This means it contains potassium (K), aluminum (Al), sulfate ions (SO₄²⁻), and water of crystallization (12H₂O).

**Hint:** Check the empirical formula against known chemical formulas for potash alum.

### Step 2: Evaluate the nature of the solution of potash alum.
- When potash alum dissolves in water, it undergoes hydrolysis.
- The aluminum ion (Al³⁺) released during hydrolysis reacts with water to produce H⁺ ions, making the solution acidic.
- Therefore, the statement that its solution is basic is incorrect.

**Hint:** Consider the hydrolysis of aluminum ions and its effect on pH.

### Step 3: Check the applications of potash alum.
- Potash alum is widely used in the dyeing industry, as well as in water purification and as a food additive.
- This statement is true.

**Hint:** Recall the various applications of potash alum in different industries.

### Step 4: Analyze the thermal behavior of potash alum.
- Upon heating, potash alum melts and loses its water of crystallization.
- This statement is also true.

**Hint:** Think about the physical properties of hydrates when heated.

### Conclusion:
After analyzing all the statements:
- The first option regarding the empirical formula is true.
- The second option stating that the solution is basic is **not true**.
- The third option about its use in the dyeing industry is true.
- The fourth option about melting upon heating is true.

Thus, the statement that is not true about potash alum is that its solution is basic.

### Final Answer:
The second option is not true: "Its solution is basic."