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H1 Chemistry

Chemistry study notes

Theories of Acids and Bases

Follow protons, calculate strong-solution pH and explain how buffers respond to change.

A-Level 8873, revised syllabus (2026-2027)

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3 topics
  1. Models and strength

    Identify roles and distinguish concentration from dissociation.

  2. pH and endpoints

    Use units and supplied titration data.

  3. Buffering and oceans

    Explain the response and its limits.

Scope and references

Learning outcomes and sources

3. Theories of Acids and Bases (8873, 2026 revision; examinations 2026 and 2027). Use the outcome map to find the explanation for a particular syllabus requirement.

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  1. 3(a) Apply the Arrhenius model.

    • Aqueous production of H+ or OH-; neutralisation.

    Follow what the acid and base actually do

  2. 3(b) Apply proton-transfer theory.

    • Bronsted-Lowry acids/bases and conjugate pairs.

    Follow what the acid and base actually do

  3. 3(c) Distinguish acid/base strength.

    • Qualitative extent of dissociation; strength versus concentration.

    Strength describes dissociation, not concentration

  4. 3(d) Explain pH and equilibrium terms.

    • pH, Ka, Kb and Kw; KaKb relation not required.

    Strength describes dissociation, not concentrationCount ions, then take the logarithm

  5. 3(e) Calculate strong-solution hydrogen concentration and pH.

    • Strong acids and strong bases; ion factors, volume units, temperature assumptions.

    Count ions, then take the logarithm

  6. 3(f) Choose titration indicators from data.

    • Transition ranges, acid/base strengths and sharp pH region.

    Choose a colour change inside the sharp rise

  7. 3(g) Explain buffers and their uses.

    • (i) Consumption of added acid/base by buffer components.
    • (ii) CO3 2-/HCO3- ocean buffer and increased atmospheric CO2 causing ocean acidification.

    Keep an acid and its conjugate base availableApply the same proton bookkeeping to the ocean