Which of the following is a "super acid "

Options

A. `(HF + SbF_5)` in `SO_2`
B. `(H_2SO_4+SO_3)` in `SO_2`
C. `(HNO_3 + BF_3)` in `SO_2`
D. `(H_3PO_4 + PF_5)` in `SO_2`

Answer

To determine which of the given options is a "super acid," we need to understand what a super acid is. A super acid is defined as an acid that has a higher proton (H⁺) chemical strength than 100% pure sulfuric acid (H₂SO₄).

Let's analyze the options provided:

1. **HF + SF₆ and SO₂**:
- HF (hydrofluoric acid) is a weak acid, and while SF₆ is a strong fluorinating agent, this combination does not produce a super acid.

2. **H₂SO₄ + SO₃**:
- The combination of sulfuric acid (H₂SO₄) and sulfur trioxide (SO₃) leads to the formation of oleum (H₂S₂O₇), which is indeed a super acid. This option is a strong contender.

3. **HNO₃ + BF₃ and SO₂**:
- HNO₃ (nitric acid) is a strong acid, but when combined with BF₃ (boron trifluoride), it does not create a super acid.

4. **H₃PO₄ + PF₅ and SO₂**:
- Phosphoric acid (H₃PO₄) is a moderate acid, and while PF₅ is a strong Lewis acid, this combination does not yield a super acid.

Now, let's summarize the findings:

- The only combination that produces a super acid is **H₂SO₄ + SO₃**, which forms oleum.

Thus, the correct answer is **H₂SO₄ + SO₃**.

### Final Answer:
The super acid among the given options is **H₂SO₄ + SO₃**.