Which of the following is not a compound?

Options

A. sulphur dioxide
B. chalk
C. lead
D. sulphuric acid

Explanation

To determine which of the following is not a compound, we need to analyze each option provided in the question. A compound is defined as a substance formed when two or more elements are chemically bonded together in a fixed ratio.

### Step-by-Step Solution:

1. **Identify the Options**: The question implies that there are multiple options to choose from. Let's consider the options mentioned in the video transcript: Sulfur Dioxide (SO2), Chalk (Calcium Carbonate - CaCO3), Lead (Pb), and Sulfuric Acid (H2SO4).

2. **Analyze Sulfur Dioxide (SO2)**:
- Composition: It consists of sulfur (S) and oxygen (O).
- Ratio: There is 1 atom of sulfur for every 2 atoms of oxygen.
- Conclusion: Since it is made of two elements in a fixed ratio, SO2 is a compound.

3. **Analyze Chalk (Calcium Carbonate - CaCO3)**:
- Composition: It consists of calcium (Ca), carbon (C), and oxygen (O).
- Ratio: The ratio is 1:1:3 (1 calcium, 1 carbon, and 3 oxygen).
- Conclusion: Since it is made of three elements in a fixed ratio, chalk is a compound.

4. **Analyze Lead (Pb)**:
- Composition: Lead is a single element.
- Ratio: There is no ratio to consider since it is not combined with any other element.
- Conclusion: Lead is not a compound because it consists of only one element and does not form any chemical bonds with other elements.

5. **Analyze Sulfuric Acid (H2SO4)**:
- Composition: It consists of hydrogen (H), sulfur (S), and oxygen (O).
- Ratio: The ratio is 2:1:4 (2 hydrogen, 1 sulfur, and 4 oxygen).
- Conclusion: Since it is made of three elements in a fixed ratio, sulfuric acid is a compound.

6. **Final Conclusion**: Among the options analyzed, Lead (Pb) is the only substance that is not a compound.

### Answer: Lead (Pb) is not a compound.

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