Question detail
What effect does increasing the concentration of a strong acid have on the pH of the solution?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Acids and bases (A-level only)
Question
- A. The pH decreases as the concentration increases.
- B. The pH increases as the concentration increases. (A-level cue 82ffccf6 distractor 1)
- C. The pH remains constant regardless of concentration. (A-level cue 82ffccf6 distractor 2)
- D. The pH first decreases, then increases with concentration. (A-level cue 82ffccf6 distractor 3)
Answer
The pH decreases as the concentration increases.
Explanation
The correct option is The pH decreases as the concentration increases.. The pH decreases as the concentration increases. is correct because it supports the objective: Distinguish acid strength from concentration.. The reasoning stays within Brønsted-Lowry acids and bases (A-level only) and avoids drifting into a similar A-Level Chemistry idea. This item is treated as conceptual revision rather than a formal calculation item because the validated answer is an explanation or option choice, not a worked numerical response.
Common mistake
Confusing Acid Strength with Concentration
Students often confuse the strength of an acid with its concentration, thinking that a more concentrated solution is always a stronger acid.
Acid strength refers to the ability of an acid to donate protons (H+ ions), while concentration refers to the amount of acid present in a given volume of solution. A strong acid completely dissociates in solution, regardless of its concentration, whereas a weak acid only partially dissociates. For example, hydrochloric acid (HCl) is a strong acid, while acetic acid (CH3COOH) is a weak acid. A concentrated solution of acetic acid may still be weaker than a dilute solution of HCl. Always assess the acid's dissociation in water to determine strength.
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