On which of the following properties does the coagulating power of an ion depend?

Options

A. Both magnitude and sign of the charge on the ion
B. Size of the ion alone
C. The magnitude of the ion alone
D. The sign of charge on the ion alone

Answer

To determine the property on which the coagulating power of an ion depends, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Coagulating Power**: Coagulating power refers to the ability of an ion to cause the aggregation of particles in a colloidal solution, leading to the formation of a precipitate.

2. **Refer to Hardy-Schulze Rule**: According to the Hardy-Schulze rule, the coagulating power of an ion is influenced by both the magnitude and the sign of the charge on the ion.

3. **Analyze the Options**:
- **Option A**: Both magnitude and sign of the charge on the ion.
- **Option B**: Size of the ion alone.
- **Option C**: Magnitude of the ion alone.
- **Option D**: Sign of the charge on the ion alone.

4. **Evaluate Each Option**:
- **Option A** is correct because it considers both the magnitude and the sign of the charge, which are crucial for coagulation.
- **Option B** is incorrect as the size of the ion does not solely determine coagulating power.
- **Option C** is incorrect because only considering the magnitude without the sign is insufficient.
- **Option D** is also incorrect as it only considers the sign of the charge.

5. **Conclusion**: Based on the analysis, the coagulating power of an ion depends on both the magnitude and the sign of the charge on the ion. Therefore, the correct answer is **Option A**.

### Final Answer:
The coagulating power of an ion depends on both the magnitude and sign of the charge on the ion (Option A).