In which of the sols, the colloidal particles are with negative charge?

Options

A. `TiO_2`
B. Haemoglobin
C. Starch
D. Hydrated `Al_2O_3`

Answer

To determine which of the sols has colloidal particles with a negative charge, we can analyze the options provided based on the principles of colloidal chemistry. Here’s a step-by-step solution:

### Step 1: Understand the Concept of Colloidal Charge
Colloidal particles can carry either a positive or negative charge. The charge can arise from two main processes:
1. **Electron Capture**: Colloidal particles can capture electrons, leading to a negative charge.
2. **Preferential Adsorption**: Certain ions in the solution can preferentially adsorb onto the surface of the colloidal particles, imparting a charge.

### Step 2: Analyze the Given Options
We need to evaluate the options based on the known charges of the colloidal particles:
- **Titanium Oxide**: Typically has a positive charge in colloidal form.
- **Hemoglobin**: Generally also has a positive charge.
- **Starch**: Known to have a negative charge when dispersed in a solution.

### Step 3: Identify the Correct Option
From the analysis:
- **Option 1 (Titanium Oxide)**: Positive charge.
- **Option 2 (Hemoglobin)**: Positive charge.
- **Option 3 (Starch)**: Negative charge.

Thus, the correct answer is **Option 3**, which contains starch with a negative charge.

### Final Answer
The sol in which the colloidal particles are negatively charged is **Option 3 (Starch)**.

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