8.1 Introduction to Acids & Bases

01pH and water

Water self-ionizes: H₂O ⇌ H⁺ + OH⁻, Kw = [H⁺][OH⁻] = 1.0 × 10^−14 at 25 °C.

pH = −log[H⁺], pOH = −log[OH⁻], pH + pOH = 14 (at 25 °C). Each pH unit is a 10× change.

[H⁺] = 10^−pH.

Worked example: [OH⁻] = 1 × 10^−4 → pOH 4 → pH 10.

Key takeaways

Watch outNeutral means [H⁺] = [OH⁻], not always pH 7.

Quick check

1.[H⁺] = 1 × 10^−5. pH?

2.pH 3 vs pH 5: how much more H⁺?

3.Kw increases with temperature. Neutral pH at 50 °C is…