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

Answer

To determine which of the given salts will turn blue litmus paper red, we need to analyze the nature of each salt in an aqueous solution. The salts provided are Sodium Sulphate (Na2SO4), Sodium Carbonate (Na2CO3), and Ammonium Sulphate (NH4)2SO4.

### Step-by-Step Solution:

1. **Identify the Nature of Each Salt**:
- **Sodium Sulphate (Na2SO4)**: This salt is formed from a strong acid (sulphuric acid, H2SO4) and a strong base (sodium hydroxide, NaOH). The resulting solution is neutral and will not affect litmus paper.
- **Sodium Carbonate (Na2CO3)**: This salt is formed from a strong base (sodium hydroxide, NaOH) and a weak acid (carbonic acid, H2CO3). The resulting solution is basic and will turn red litmus paper blue.
- **Ammonium Sulphate ((NH4)2SO4)**: This salt is formed from a weak base (ammonium hydroxide, NH4OH) and a strong acid (sulphuric acid, H2SO4). The resulting solution is acidic and will turn blue litmus paper red.

2. **Conclusion**:
- Among the three salts, only Ammonium Sulphate ((NH4)2SO4) will turn blue litmus paper red because it is an acidic salt formed from a strong acid and a weak base.

### Final Answer:
The aqueous solution of Ammonium Sulphate ((NH4)2SO4) will turn blue litmus paper red.