pH comparison and acidity scale:\nTwo aqueous solutions are labeled A1 (pH = 2) and A2 (pH = 6). Which statement best quantifies their relative acidity/alkalinity?

Introduction / Context:
The pH scale is logarithmic: pH = −log10[H+]. Each one-unit change in pH corresponds to a tenfold change in hydrogen-ion concentration. Understanding this helps compare the strength of acidity or basicity between solutions quickly and precisely.

Given Data / Assumptions:

• Solution A1: pH = 2 → [H+] = 10^−2 mol/L.
• Solution A2: pH = 6 → [H+] = 10^−6 mol/L.
• Both are aqueous solutions at comparable conditions; activity effects neglected for simplicity.

Concept / Approach:
Relative acidity is determined by the ratio of hydrogen-ion concentrations. A difference of 4 pH units means a factor of 10^4 between [H+] values. Lower pH corresponds to higher [H+], hence higher acidity.

Step-by-Step Solution:
Compute [H+] for A1: 10^−2.Compute [H+] for A2: 10^−6.Take the ratio: (10^−2) / (10^−6) = 10^(−2 + 6) = 10^4 = 10,000.Therefore, A1 is 10,000 times more acidic (greater [H+]) than A2.

Verification / Alternative check:
The pOH or hydroxide concentration would show the inverse trend: A2 is more basic than A1 by the same factor, consistent with pH + pOH ≈ 14 at 25°C for dilute aqueous solutions.

Why Other Options Are Wrong:
“A2 is more acidic”: contradicts the pH values (higher pH means less acidic).“A1 is very slightly acidic”: pH 2 corresponds to strong acidity, not slight.“Both (a) and (c)”: includes a false statement, so the combined option is incorrect.

Common Pitfalls:
Forgetting the logarithmic nature of pH; thinking a 1-unit change is small when it is a tenfold change in [H+]; mixing up acidity with alkalinity.

Final Answer:
A1 is 10,000 times more acidic than A2.