Question

Which acid-base chemical reaction is irreversible?
water on its own
strong acid added to water
weak acid added to water
weak base added to water

Answer 1

In acid-base reactions, the reversibility can depend on the strengths of the acids and bases involved.

1. **Water on its own:** This is not an acid-base reaction. Water is a neutral substance.

2. **Strong acid added to water:** This reaction is generally considered irreversible. Strong acids, such as hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), ionize completely in water, producing a high concentration of hydrogen ions (H⁺). The completion of ionization means that the reverse reaction (recombination of ions to form the original acid) is not significant under normal conditions.

3. **Weak acid added to water:** Weak acids only partially ionize in solution, making this reaction reversible. For example, acetic acid (CH₃COOH) will establish an equilibrium between undissociated acetic acid and its ions (H⁺ and CH₃COO⁻).

4. **Weak base added to water:** Similar to weak acids, weak bases also partially ionize in solution, creating an equilibrium. For example, ammonia (NH₃) will only partially accept protons from water, establishing a reversible reaction.

Thus, the **strong acid added to water** is the acid-base reaction that is generally considered irreversible.