To coagulate gelatin sol, which of the following is most effective ?

Options

A. NaCl
B. `Na_(3)PO_(4)`
C. `AlCl_(3)`
D. Alcohol

Answer

To determine which compound is most effective in coagulating a gelatin sol, we need to understand the concept of coagulation and the charges involved.

### Step-by-Step Solution:

1. **Understand Coagulation**:
- Coagulation is the process of converting a liquid into a semi-solid or solid state. In the context of colloids, it refers to the aggregation of particles, leading to the formation of a precipitate.

**Hint**: Coagulation is essentially the process of thickening or solidifying a liquid.

2. **Identify the Charge of Gelatin**:
- Gelatin is negatively charged. This means that it will be attracted to positively charged ions (cations) in a solution.

**Hint**: Remember that opposite charges attract; negatively charged particles will be coagulated by positively charged ions.

3. **Determine the Effectiveness of Coagulation**:
- The effectiveness of coagulation increases with the charge of the cation. Higher charged cations will lead to more effective coagulation of the negatively charged gelatin.

**Hint**: Look for cations with higher positive charges to enhance coagulation.

4. **Analyze the Given Compounds**:
- The compounds provided are:
- NaCl: Dissociates into Na⁺ (charge +1) and Cl⁻.
- Trisodium phosphate: Dissociates into Na⁺ (charge +1) and phosphate ions.
- Aluminium trichloride (AlCl₃): Dissociates into Al³⁺ (charge +3) and Cl⁻.
- Alcohol: Does not dissociate into ions.

**Hint**: Focus on the cations produced when the compounds dissociate.

5. **Compare the Charges**:
- Na⁺ and the ions from trisodium phosphate have a charge of +1.
- Al³⁺ from aluminium trichloride has a charge of +3.
- Since Al³⁺ has a higher positive charge, it will be more effective in coagulating the negatively charged gelatin.

**Hint**: The greater the positive charge of the cation, the more effective it will be in coagulating gelatin.

6. **Conclusion**:
- Among the given compounds, aluminium trichloride (AlCl₃) is the most effective in coagulating gelatin due to its Al³⁺ ions.

**Final Answer**: The most effective compound for coagulating gelatin sol is **Aluminium trichloride (AlCl₃)**.