Which of the following gives the correct increasing order of acid strength?

Options

A. water `lt` acetic acid `lt` hydrochloric acid
B. water `lt` hydrochloric acid `lt` acetic acid
C. Acetic acid `lt` water `lt` hydrochloric acid
D. Hydrochloric acid `lt` water `lt` acetic acid

Explanation

To determine the correct increasing order of acid strength among hydrochloric acid (HCl), acetic acid (CH₃COOH), and water (H₂O), we need to analyze the properties of each substance.

### Step-by-Step Solution:

1. **Identify the Acids:**
- Hydrochloric acid (HCl)
- Acetic acid (CH₃COOH)
- Water (H₂O)

2. **Understand Acid Strength:**
- Acid strength is determined by the ability of an acid to donate protons (H⁺ ions) in solution.
- Strong acids completely dissociate in water, while weak acids only partially dissociate.

3. **Analyze Hydrochloric Acid (HCl):**
- HCl is a strong acid. It completely ionizes in water to produce H⁺ and Cl⁻ ions.
- This means it has a very low pH (typically around 0-1 for concentrated solutions).

4. **Analyze Acetic Acid (CH₃COOH):**
- Acetic acid is a weak acid. It only partially ionizes in water.
- The ionization of acetic acid can be represented as:
\[ \text{CH}_3\text{COOH} \rightleftharpoons \text{H}^+ + \text{CH}_3\text{COO}^- \]
- The pH of acetic acid solutions is typically between 4-6, indicating it is weaker than HCl.

5. **Analyze Water (H₂O):**
- Water is neutral and does not act as an acid in this context. Its pH is 7.
- It does not donate protons in the same way acids do.

6. **Establish the Order of Strength:**
- Based on the analysis:
- Strongest acid: Hydrochloric acid (HCl)
- Moderate acid: Acetic acid (CH₃COOH)
- Weakest: Water (H₂O)

7. **Final Increasing Order of Acid Strength:**
- The correct increasing order of acid strength is:
\[ \text{H}_2\text{O} < \text{CH}_3\text{COOH} < \text{HCl} \]

### Conclusion:
The increasing order of acid strength is water (H₂O) < acetic acid (CH₃COOH) < hydrochloric acid (HCl).