Which of the following is an acid?

Options

A. CH4
B. NaCl
C. NaOH
D. HNO3

Answer

To determine which of the given options is an acid, we need to analyze each option based on the definition of an acid. An acid is a substance that can donate protons (H⁺ ions) in a solution.

### Step-by-Step Solution:

1. **Analyze Option 1: Methane (CH₄)**
- Methane is a simple hydrocarbon consisting of one carbon atom and four hydrogen atoms.
- It is a gas at room temperature and does not have the ability to donate H⁺ ions.
- **Conclusion**: Methane is not an acid.

2. **Analyze Option 2: Sodium Chloride (NaCl)**
- Sodium chloride is a salt formed from the neutralization reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH).
- It does not have the ability to donate H⁺ ions in solution.
- **Conclusion**: Sodium chloride is not an acid.

3. **Analyze Option 3: Sodium Hydroxide (NaOH)**
- Sodium hydroxide is a strong base that dissociates in water to produce hydroxide ions (OH⁻).
- It does not donate H⁺ ions; instead, it can accept protons.
- **Conclusion**: Sodium hydroxide is not an acid.

4. **Analyze Option 4: Nitric Acid (HNO₃)**
- Nitric acid is a well-known strong acid.
- It dissociates in water to produce H⁺ ions and nitrate ions (NO₃⁻).
- **Conclusion**: Nitric acid is indeed an acid because it donates H⁺ ions.

### Final Answer:
Among the given options, **HNO₃ (Nitric Acid)** is the acid.

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