Question

answer the following questions. how does increasing the concentration of H3O^+ ions affect the pH of a solution? as you increase the concentration of H3O^+ ions in a solution, does this indicate the solution is an acid or a base and what does it tell you about strength of the acid or base?

Answer 1

- pH is defined as pH = −log10[H3O+]. So increasing the hydronium ion concentration ([H3O+]) makes the pH smaller (more acidic).
- Example: [H3O+] = 1.0×10−3 M → pH = 3.0. If [H3O+] increases to 2.0×10−3 M, pH = −log10(2.0×10−3) ≈ 2.70 (a decrease of ~0.30).

- Whether the solution is an acid or base: a higher [H3O+] than neutral (at 25 °C neutral is 1.0×10−7 M, pH 7) means the solution is acidic. Lower [H3O+] than neutral means basic.

- What [H3O+] tells you about acid/base strength: the measured [H3O+] tells you how acidic the solution is, but it does not by itself tell you whether the acid is strong or weak.
- "Strength" refers to how completely an acid dissociates (its Ka). A strong acid at a given concentration essentially fully dissociates and produces a large [H3O+]. A weak acid at the same concentration only partially dissociates and produces a smaller [H3O+].
- Conversely, a high [H3O+] could come from a concentrated weak acid or a dilute strong acid; you need information about initial concentration and Ka (or the identity of the acid) to judge strength.

- Quick note: Kw = [H3O+][OH−] (≈1.0×10−14 at 25 °C), so changes in [H3O+] are inversely reflected in [OH−]. Also, at high ionic strength or nonstandard temperatures, activities (not just concentrations) matter for precise pH.