Science (086) — AI-generated practice question

HCl (hydrochloric acid) is the stronger acid.

HCl is a mineral acid that is completely ionised in water, producing a large number of H⁺ ions. Acetic acid (CH₃COOH), being a carboxylic acid, is a weak acid — it only partially ionises in water, producing fewer H⁺ ions at the same concentration.

Since acid strength depends on the number of H⁺ ions produced, HCl is stronger than CH₃COOH at equal concentrations.

Comparison of pH: At the same concentration, HCl produces more H⁺ ions, so it has a lower pH than acetic acid. Acetic acid, being partially ionised, produces fewer H⁺ ions and therefore has a higher pH than HCl.

Source: Chapter 2, Section 2.3; Chapter 4, Section 4.4.2

---

• The key phrase from the textbook is: "unlike mineral acids like HCl, which are completely ionised, carboxylic acids are weak acids." Quote or paraphrase this directly — examiners look for it.
• Connect acid strength to H⁺ ion concentration (more H⁺ = stronger acid = lower pH). This links Chapter 2 (pH scale) with Chapter 4 (acetic acid properties).
• Don't just state which is stronger — explain why (ionisation) and compare pH as the question asks both. All three points carry marks.