Q1. [1] medium exam-ready
Assertion (A): When an aqueous solution of an acid is diluted, its pH value increases.
Reason (R): Dilution decreases the concentration of H₃O⁺ ions per unit volume of the solution.
- A Both A and R are true and R is the correct explanation of A.
- B Both A and R are true but R is not the correct explanation of A.
- C A is true but R is false.
- D A is false but R is true.
Generated by claude-sonnet-4-6 · 2026-06-26 01:03 · grounding rag
Model Answer
Option A is correct. Both A and R are true and R is the correct explanation of A.
On dilution, concentration of H₃O⁺ ions per unit volume decreases, so pH increases (higher pH = lower H⁺ concentration).
Explanation
- The textbook states: "Mixing an acid or base with water results in decrease in the concentration of ions (H₃O⁺/OH⁻) per unit volume" — this confirms R is true.
- The pH scale states: "Higher the hydronium ion concentration, lower is the pH value" — so decreasing H₃O⁺ concentration directly causes pH to rise, confirming A is true AND that R correctly explains A.
- Choose A, not B, because R is the direct/causal explanation of A.