Question

 A few sols are given below:
As₂S₃ sol, starch sol, Al₂O₃ ·
xH₂O sol, TiO₂ sol, gold sol, congo red sol, blood, methylene blue sol, CdS sol
The number of positively charged sols in the above list is:

• A. \( 4 \)
• B. \( 5 \)
• C. \( 6 \)
• D. \( 7 \)

Hint:

- Metal oxides and hydroxides generally form positively charged sols.
- Metal sulfides and dyes tend to form negatively charged sols.
- Understanding colloidal charge properties helps in applications like coagulation and electrophoresis.

Answer 1

The Correct Option is A

Step 1: Understanding Colloidal Sols and Charge 
- Colloidal sols can be positively or negatively charged based on the adsorption of ions from the dispersion medium. 
- Positively charged sols typically contain metal oxides or hydroxides, while negatively charged sols include metal sulfides and organic dyes. 

Step 2: Identifying Positively Charged Sols From the given list, the positively charged sols are: 1. \( Al_2O_3 \cdot xH_2O \) (Alumina sol) 2. \( TiO_2 \) (Titanium dioxide sol) 3. Blood 4. Methylene blue sol 

Step 3: Conclusion 
- The number of positively charged sols is 4. 
- Hence, the correct answer is Option (1) 4.