Concentrated sulphuric acid is:

Options

A. efforescent
B. hygroscopic
C. oxidising agent
D. sulphonating agent

Answer

To determine the properties of concentrated sulfuric acid (H₂SO₄), we can analyze the characteristics mentioned in the question. Here’s a step-by-step breakdown of the properties of concentrated sulfuric acid:

### Step 1: Understand Efflorescent
- **Definition**: Efflorescent refers to the spontaneous loss of water from a hydrated salt.
- **Application to H₂SO₄**: Since concentrated sulfuric acid is not a hydrated salt but a strong acid, it does not exhibit efflorescence. Therefore, this property does not apply to concentrated sulfuric acid.

### Step 2: Understand Hygroscopic
- **Definition**: Hygroscopic substances are those that can absorb moisture from the environment.
- **Application to H₂SO₄**: Concentrated sulfuric acid is highly hygroscopic. It has a strong affinity for water and readily absorbs moisture from the air. Thus, this property is applicable to concentrated sulfuric acid.

### Step 3: Understand Oxidizing Agent
- **Definition**: An oxidizing agent is a substance that can accept electrons from another substance, thereby oxidizing it while reducing itself.
- **Application to H₂SO₄**: Concentrated sulfuric acid acts as a strong oxidizing agent. Upon heating, it can release oxygen and oxidize non-metals. For example, when carbon reacts with concentrated sulfuric acid, it is oxidized to carbon dioxide (CO₂), while sulfuric acid is reduced. Therefore, this property is also applicable to concentrated sulfuric acid.

### Step 4: Understand Sulfonating Agent
- **Definition**: A sulfonating agent introduces a sulfonic acid group (-SO₃H) into an organic compound.
- **Application to H₂SO₄**: Concentrated sulfuric acid can act as a sulfonating agent. For instance, when it reacts with benzene, it introduces a sulfonic acid group, forming benzene sulfonic acid. Hence, this property is applicable to concentrated sulfuric acid.

### Conclusion
Based on the analysis:
- Concentrated sulfuric acid is **not efflorescent**.
- It is **hygroscopic**.
- It is a **strong oxidizing agent**.
- It is a **sulfonating agent**.

### Summary of Properties
1. **Efflorescent**: No
2. **Hygroscopic**: Yes
3. **Oxidizing Agent**: Yes
4. **Sulfonating Agent**: Yes