Which of the following statement is correct for oleum ?

Options

A. It is prepared by adsorption of `SO_(3) ` in conc. `H_(2)SO_(4)`
B. It contains O–O groups
C. It has six OH groups
D. None of these

Explanation

To solve the question regarding oleum, we need to evaluate the given statements one by one:

### Step 1: Analyze Option 1
**Statement:** "It is prepared by adsorption of SO3 in concentrated H2SO4."

**Explanation:** Oleum is indeed formed by the reaction of sulfur trioxide (SO3) with concentrated sulfuric acid (H2SO4). The process involves the adsorption of SO3 gas into concentrated H2SO4, resulting in the formation of oleum, which can be represented as H2S2O7 (pyrosulfuric acid).

**Conclusion:** This statement is correct.

### Step 2: Analyze Option 2
**Statement:** "It contains O-O groups."

**Explanation:** The structure of oleum does not contain O-O (oxygen-oxygen) bonds. In oleum, the structure consists of sulfur atoms bonded to oxygen atoms, but there are no direct O-O bonds present.

**Conclusion:** This statement is incorrect.

### Step 3: Analyze Option 3
**Statement:** "It has 6 OH groups."

**Explanation:** Upon examining the structure of oleum, we find that it contains only 2 hydroxyl (OH) groups. Therefore, the claim of having 6 OH groups is not accurate.

**Conclusion:** This statement is incorrect.

### Step 4: Analyze Option 4
**Statement:** "None of these."

**Explanation:** Since we have already established that Option 1 is correct, this statement cannot be true.

**Conclusion:** This statement is incorrect.

### Final Answer
The correct statement regarding oleum is **Option 1: It is prepared by adsorption of SO3 in concentrated H2SO4.**

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