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Acids and bases (A-level only)
This A-level-only topic develops quantitative and qualitative acid-base chemistry.
20
Objectives
10
Flashcards
10
Questions
90 min
Study time
AqaA LevelChemistryPhysical chemistry
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Syllabus checklist
What you need to know
20 objective pages available
Brønsted-Lowry acids and bases (A-level only)4 objectives
- Define Brønsted-Lowry acids and bases.
- Identify conjugate acid-base pairs.
- Write equations showing proton transfer.
- Distinguish acid strength from concentration.
pH and Kw (A-level only)4 objectives
- Calculate pH from hydrogen ion concentration.
- Calculate hydrogen ion concentration from pH.
- Use Kw to calculate hydrogen ion or hydroxide ion concentrations.
- Apply pH calculations to strong acids and strong bases.
Weak acids, Ka and pKa (A-level only)4 objectives
- Construct Ka expressions for weak acids.
- Calculate pH of a weak acid from concentration and Ka.
- Convert between Ka and pKa.
- Explain weak-acid behaviour in terms of partial dissociation.
pH curves, titrations and indicators (A-level only)4 objectives
- Perform calculations using acid-base titration data.
- Sketch and explain pH curves for combinations of weak and strong monoprotic acids and bases.
- Select suitable indicators using pH curves and transition ranges.
- Required practical: investigate pH changes in weak acid and strong base or strong acid and weak base titrations.
Buffer action (A-level only)4 objectives
- Explain qualitatively how acidic buffers resist pH change.
- Explain qualitatively how basic buffers resist pH change.
- Calculate the pH of acidic buffer solutions.
- Explain applications of buffer solutions.
Key terms
Brønsted-Lowry acidBrønsted-Lowry baseConjugate acidConjugate baseProton TransferEquilibrium Constant (Kc)Acid StrengthAcid ConcentrationHydrogen ion concentrationpH scaleAcidBase
Exam tips
- Use clear definitions: Always define Brønsted-Lowry acids and bases clearly in your answers.
- Practice identifying conjugate pairs: Regularly practice identifying conjugate acid-base pairs in different reactions.
Common mistakes
- Confusing acids and bases: Remember that acids donate protons while bases accept protons.
- Confusing conjugate acids and bases: Remember that the conjugate acid is formed when a base gains a proton, while the conjugate base is formed when an acid loses a proton.
Practice preview
- Which of the following statements correctly defines a Brønsted-Lowry acid?
- Explain how the Brønsted-Lowry theory expands upon the Arrhenius definition of acids and bases.
- In a reaction between hydrochloric acid (HCl) and ammonia (NH3), identify the Brønsted-Lowry acid and base. Write the equation for the reaction.
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