Acetic acid is weak acid because

Options

A. it is unstable
B. It is an organic aliphatic acid
C. it is slightly ionised
D. None of the above

Explanation

**Step-by-Step Solution:**

1. **Definition of Weak Acid**: A weak acid is defined as an acid that does not completely dissociate into its ions in an aqueous solution. This means that when a weak acid is dissolved in water, only a fraction of the acid molecules ionize.

2. **Chemical Formula of Acetic Acid**: The chemical formula of acetic acid is CH₃COOH. This is important to identify the compound we are discussing.

3. **Dissociation of Acetic Acid**: When acetic acid is added to water, it does not dissociate completely. Instead, it establishes an equilibrium between the undissociated acetic acid molecules and the ions produced (acetate ions CH₃COO⁻ and hydrogen ions H⁺).

4. **Comparison with Strong Acids**: In contrast, strong acids (like hydrochloric acid, HCl) dissociate completely in water, meaning all the acid molecules break apart into ions. This complete dissociation is what characterizes a strong acid.

5. **Conclusion**: Since acetic acid only partially ionizes in water, it is classified as a weak acid. Therefore, the reason acetic acid is considered a weak acid is that it is "slightly ionized" in solution.

6. **Correct Option**: Among the provided options, the correct answer is that acetic acid is "slightly ionized."

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