Which of the following statements regarding conc. Sulphuric acid is not correct?

Options

A. It is reduced to `SO_2` on reaction with Cu.
B. It is a strong dehydrating agent.
C. It can be used to manufacture more volatile acids from their corresponding salts.
D. The absorption of `SO_2` is sulphuric acid produces oleum.

Answer

To determine which statement regarding concentrated sulfuric acid is not correct, let's analyze each option step by step.

### Step 1: Analyze the first statement
**Statement:** "It is reduced to sulfur dioxide on reaction with copper."

**Analysis:** When concentrated sulfuric acid (H₂SO₄) reacts with copper (Cu), it indeed gets reduced to sulfur dioxide (SO₂). The reaction can be represented as:
\[ \text{Cu} + 2 \text{H}_2\text{SO}_4 \rightarrow \text{CuSO}_4 + SO_2 + 2 \text{H}_2\text{O} \]
This statement is **correct**.

### Step 2: Analyze the second statement
**Statement:** "It is a strong dehydrating agent."

**Analysis:** Concentrated sulfuric acid is well-known for its strong dehydrating properties. It can remove water from substances, making this statement **correct**.

### Step 3: Analyze the third statement
**Statement:** "It can be used to manufacture more volatile acids from their corresponding salt."

**Analysis:** Concentrated sulfuric acid can indeed be used to produce more volatile acids (like hydrochloric acid) from their salts through a process called acid-base reaction. Therefore, this statement is also **correct**.

### Step 4: Analyze the fourth statement
**Statement:** "Absorption of sulfur dioxide in sulfuric acid produces oleum."

**Analysis:** This statement is incorrect. The correct process involves the absorption of sulfur trioxide (SO₃) in sulfuric acid to produce oleum (H₂S₂O₇). The reaction is:
\[ \text{SO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{H}_2\text{S}_2\text{O}_7 \]
Thus, this statement is **not correct**.

### Conclusion
The statement that is not correct regarding concentrated sulfuric acid is:
**"Absorption of sulfur dioxide in sulfuric acid produces oleum."**

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