Which of the following is/are pure substance(s)?

Options

A. CuSO4.5H2O
B. Brass
C. Diamond
D. All of these

Answer

To determine which of the given options are pure substances, we need to understand the definition of a pure substance. A pure substance is a material that has a constant composition and consistent properties throughout the sample. It can be an element or a compound.

Let's analyze the given options step by step:

1. **CuSO4·5H2O (Copper(II) sulfate pentahydrate)**:
- This compound consists of copper, sulfur, oxygen, and water molecules in a fixed ratio.
- Its composition is constant, and it can be broken down into its elements through chemical reactions.
- Therefore, **CuSO4·5H2O is a pure substance**.

2. **Brass**:
- Brass is an alloy made from a mixture of copper and zinc.
- Since it is a mixture and does not have a fixed composition (the ratio of copper to zinc can vary), it is not a pure substance.
- Therefore, **Brass is not a pure substance**.

3. **Diamond**:
- Diamond is an allotrope of carbon, meaning it is a form of carbon that has a specific structure and composition.
- It consists entirely of carbon atoms arranged in a crystal lattice, which gives it consistent properties.
- Therefore, **Diamond is a pure substance**.

In conclusion, the pure substances among the options are **CuSO4·5H2O and Diamond**.

### Summary:
- **CuSO4·5H2O**: Pure substance (compound).
- **Brass**: Not a pure substance (mixture).
- **Diamond**: Pure substance (element).