hardy - Schulze law states that :

Options

A. solution must have higher gold number
B. disperse phase and dispersion medium must be of the same sign
C. micelles coagulate in presence of surfactants
D. the ions carrying more opposite charge to that of sol particle are effective in coagulation

Answer

**Step-by-Step Solution:**

1. **Understanding Hardy-Schulze Law:**
The Hardy-Schulze law is a principle in colloid chemistry that describes the coagulation of colloidal particles. It states that the effectiveness of an ion in causing coagulation is directly related to its charge.

2. **Valency of Ions:**
According to Hardy-Schulze law, the greater the valency of the flocculating ion (the ion that causes coagulation), the greater its ability to cause precipitation or coagulation of the colloidal particles. This means that ions with higher charges are more effective at neutralizing the charge of the colloidal particles.

3. **Coagulation Power:**
For example, if we compare ions such as Al³⁺, Ba²⁺, and Na⁺:
- Al³⁺ has a charge of +3.
- Ba²⁺ has a charge of +2.
- Na⁺ has a charge of +1.
The ion Al³⁺ will have a stronger coagulating power than Ba²⁺, which in turn has a stronger coagulating power than Na⁺. This is because Al³⁺ can neutralize the charge of more particles due to its higher charge.

4. **Conclusion:**
Based on the explanation above, the correct statement according to Hardy-Schulze law is that "the ions carrying more opposite charge to that of the solution particles are effective in coagulation." Therefore, the correct option is option 4.

**Final Answer:**
The Hardy-Schulze law states that the ions carrying more opposite charge to that of the solution particles are effective in coagulation.

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