Consider the following salts :
Sodium sulphate, Sodium carbonate, Ammonium sulphate
The aqueous solution of which of these salts will:
turn phenolphthalein to pink ?

Answer

To determine which of the given salts will turn phenolphthalein to pink, we need to analyze the nature of each salt in an aqueous solution. Phenolphthalein is an indicator that turns pink in basic solutions.

### Step-by-Step Solution:

1. **Identify the Salts**: The salts given are Sodium Sulphate (Na2SO4), Sodium Carbonate (Na2CO3), and Ammonium Sulphate (NH4SO4).

2. **Understand the Nature of Each Salt**:
- **Sodium Sulphate (Na2SO4)**:
- Sodium Sulphate is formed from a strong base (NaOH) and a strong acid (H2SO4).
- When dissolved in water, it does not produce a basic solution; hence it is neutral.

- **Sodium Carbonate (Na2CO3)**:
- Sodium Carbonate is formed from a strong base (NaOH) and a weak acid (H2CO3).
- When dissolved in water, it hydrolyzes to form NaOH, which is a strong base. Therefore, the solution is basic, and it will turn phenolphthalein pink.

- **Ammonium Sulphate (NH4SO4)**:
- Ammonium Sulphate is formed from a weak base (NH4OH) and a strong acid (H2SO4).
- When dissolved in water, it produces an acidic solution, hence it will not turn phenolphthalein pink.

3. **Conclusion**:
- Among the three salts, only Sodium Carbonate (Na2CO3) produces a basic solution when dissolved in water. Therefore, it will turn phenolphthalein to pink.

### Final Answer:
The aqueous solution of **Sodium Carbonate (Na2CO3)** will turn phenolphthalein to pink.

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