Cell voltages and half-cell potentials are often compeared under standard conditions called the standard state at a specified temperature (298K). The standard state requires all reagents to be pure with all gases at unit fugacity, all ions at unit activity and all electrical connections between half-cells to be made with platinum. Suppose following are half cell reaction, with respective emf (s) are -0.25 V and -0.3V.
Cell reaction I `underset("1 atm")(Pt(H_(2))|HCl)`
Cell reaction II `underset("1 atm")(Pt(H_(2))|H_(2)SO_(4))`
Zinc gives `H_2` with `H_2SO_4` and HCI but not with HNO3 because:

Options

A. zinc acts as oxidizing agent when reacts with `HNO_3`
B. `HNO_3` is a weaker acid than `H_2SO_4 and HCI`
C. in electrochemical series zinc is above than hydrogen
D. `NO_(3)^(-)` is reduced in preference to hydronium ion

Answer

To solve the question regarding why zinc reacts with sulfuric acid (H₂SO₄) and hydrochloric acid (HCl) to produce hydrogen gas but does not react with nitric acid (HNO₃) to produce hydrogen gas, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reactivity of Acids**:
- Zinc (Zn) is a reactive metal that can displace hydrogen from acids. When zinc reacts with acids like HCl and H₂SO₄, it produces hydrogen gas (H₂) and zinc salts.

2. **Reactions with Hydrochloric Acid (HCl)**:
- The reaction of zinc with hydrochloric acid is as follows:
\[ \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow \]
- Here, zinc displaces hydrogen ions (H⁺) from HCl, resulting in the formation of hydrogen gas.

3. **Reactions with Sulfuric Acid (H₂SO₄)**:
- The reaction of zinc with sulfuric acid is:
\[ \text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2 \uparrow \]
- Similar to HCl, zinc displaces hydrogen ions from sulfuric acid, producing hydrogen gas.

4. **Reactions with Nitric Acid (HNO₃)**:
- When zinc reacts with nitric acid, the reaction is different:
\[ \text{Zn} + 4\text{HNO}_3 \rightarrow \text{Zn(NO}_3\text{)}_2 + 2\text{NO}_2 + 2\text{H}_2\text{O} \]
- In this case, instead of producing hydrogen gas, zinc reduces the nitrate ions (NO₃⁻) to nitrogen dioxide (NO₂) gas.

5. **Reason for No Hydrogen Production**:
- The key reason why zinc does not produce hydrogen gas with nitric acid is that nitric acid is a strong oxidizing agent. It preferentially oxidizes zinc instead of allowing it to reduce the hydrogen ions (H⁺) to hydrogen gas (H₂). Therefore, the nitrate ions are reduced to nitrogen dioxide instead.

6. **Conclusion**:
- Zinc reacts with HCl and H₂SO₄ to produce hydrogen gas because these acids do not act as oxidizing agents. In contrast, nitric acid acts as a strong oxidizing agent, leading to the reduction of nitrate ions rather than hydrogen ions.

### Final Answer:
Zinc gives hydrogen gas with HCl and H₂SO₄ but not with HNO₃ because nitric acid is a strong oxidizing agent that reduces nitrate ions instead of allowing the reduction of hydrogen ions.