Which one of the following statements is not correct ?

Options

A. Tyndall effect in colloidal solution solution is due to scattering of light
B. Hardy - Schuize rule is applicable only to the coagulation of lyophilic sols
C. Bule colour of the sky is due to scattering of light by dust particies
D. Greater flocculation value on an electrolyte means its poor coagulating power

Answer

To solve the question "Which one of the following statements is not correct?", we will analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Analyze the First Statement:**
- **Statement:** "Tyndall effect in colloidal solution is due to scattering of light."
- **Explanation:** This statement is correct. The Tyndall effect occurs when light is scattered by colloidal particles, making the path of the light visible.

2. **Analyze the Second Statement:**
- **Statement:** "Hardy-Schulz rule is applicable only to the coagulation of lyophilic salts."
- **Explanation:** This statement is incorrect. The Hardy-Schulz rule applies to both lyophilic and lyophobic colloids. It states that the greater the valency of the coagulating ion, the greater its coagulating power.

3. **Analyze the Third Statement:**
- **Statement:** "Blue color of sky is due to scattering of light by dust particles."
- **Explanation:** This statement is correct. The blue color of the sky is due to Rayleigh scattering, which occurs when light is scattered by small particles in the atmosphere, including dust.

4. **Analyze the Fourth Statement:**
- **Statement:** "Greater flocculation value of an electrolyte means its poor coagulating power."
- **Explanation:** This statement is correct. A higher flocculation value indicates that the electrolyte has a lower coagulating power, as coagulating power is inversely proportional to flocculation value.

### Conclusion:
After analyzing all the statements, we find that the second statement is not correct. Therefore, the answer to the question is:

**Answer:** The incorrect statement is the second one: "Hardy-Schulz rule is applicable only to the coagulation of lyophilic salts."

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