Calcium sulphate is found in nature in two forms, anhydrous calcium sulphate and hydrated calcium sulphate. When anhydrous calcium sulphate is heated with coke, sulphur dioxide gas is obtained. When hydrated calcium suphate is heated to `200^(@)`C, it forms anhydrous salt.
Q. When calcium sulphate is mixed with conc. HCl and the paste is formed. What colour is obtained wehn a pinch of this paste is brought near the flame?

Options

A. golden yellow
B. brick red
C. crimson red
D. apple green

Answer

To solve the question regarding the color obtained when a pinch of the paste formed by mixing calcium sulfate with concentrated HCl is brought near a flame, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When calcium sulfate (CaSO₄) is mixed with concentrated hydrochloric acid (HCl), a paste is formed. This reaction does not produce a significant change in the chemical composition of calcium sulfate but prepares it for flame testing.

2. **Flame Test Principle**:
- A flame test is a qualitative analysis technique used to identify the presence of certain metal ions based on the characteristic color they emit when heated in a flame.

3. **Identifying Calcium**:
- Calcium (Ca) is one of the metal ions that can be identified using a flame test. The characteristic color of calcium when subjected to a flame is brick red.

4. **Performing the Flame Test**:
- When a pinch of the paste (which contains calcium ions) is brought near the flame, the heat excites the electrons in the calcium ions. As these electrons return to their ground state, they release energy in the form of light.

5. **Observing the Color**:
- The light emitted by the excited calcium ions is observed as a brick red color.

6. **Conclusion**:
- Therefore, when a pinch of the paste formed by mixing calcium sulfate with concentrated HCl is brought near the flame, the color obtained is brick red.

### Final Answer:
The color obtained when a pinch of the paste is brought near the flame is **brick red**.