Which one is the weakest acid

Options

A. `HNO_(3)`
B. `HClO_(4)`
C. `H_(2)SO_(4)`
D. HBr

Explanation

To determine which of the given acids is the weakest, we will analyze the acids based on their oxidation states and the nature of their bonds. The acids in question are HNO3 (Nitric acid), HClO4 (Perchloric acid), H2SO4 (Sulfuric acid), and HBr (Hydrobromic acid).

### Step-by-Step Solution:

1. **Identify the Acids**:
- HNO3 (Nitric acid)
- HClO4 (Perchloric acid)
- H2SO4 (Sulfuric acid)
- HBr (Hydrobromic acid)

2. **Determine the Oxidation States**:
- For HNO3: Nitrogen (N) has an oxidation state of +5.
- For HClO4: Chlorine (Cl) has an oxidation state of +7.
- For H2SO4: Sulfur (S) has an oxidation state of +6.
- For HBr: Bromine (Br) has an oxidation state of -1.

3. **Analyze Acidic Strength Based on Oxidation States**:
- Generally, as the oxidation state of the central atom in the acid increases, the acidic strength increases. Therefore, we can rank the acids based on their oxidation states:
- HClO4 (+7) > H2SO4 (+6) > HNO3 (+5) > HBr (-1)

4. **Consider the Bonding**:
- In HClO4, H2SO4, and HNO3, the hydrogen atom is bonded to oxygen. The bond between oxygen and hydrogen (O-H bond) is generally weaker, allowing for easier release of H+ ions.
- In HBr, the hydrogen is bonded to bromine, which has a stronger bond compared to the O-H bond. This means HBr can release H+ ions more easily than the others.

5. **Rank the Acids**:
- Based on the oxidation states and the nature of the bonds:
- HBr is the strongest acid.
- HClO4 is the second strongest.
- H2SO4 is next.
- HNO3 is the weakest acid.

6. **Conclusion**:
- The weakest acid among the given options is **HNO3**.

### Final Answer:
The weakest acid is **HNO3**.