AP Exam Prep · AP Chemistry
AP Chemistry Unit 8 Practice Test: Acids and Bases
Unit 8 is the second most heavily weighted unit. You will calculate pH for strong and weak acids and bases, explain buffers and titration curves, and connect molecular structure to acid strength.
- Exam weighting:
- 11–15%
- Questions:
- 13 multiple choice
- Time:
- about 17 minutes
- Cost:
- Free, no sign-up
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What AP Chem Unit 8 covers
Unit 8, Acids and Bases, makes up 11–15% of the multiple-choice section and usually takes ~14–16 class periods. These are the topics in the current course framework, and every question in the test above is tagged with one of them.
- 8.1Introduction to Acids and Bases
- 8.2pH and pOH of Strong Acids and Bases
- 8.3Weak Acid and Base Equilibria
- 8.4Acid-Base Reactions and Buffers
- 8.5Acid-Base Titrations
- 8.6Molecular Structure of Acids and Bases
- 8.7pH and pKa
- 8.8Properties of Buffers
- 8.9Henderson-Hasselbalch Equation
- 8.10Buffer Capacity
- 8.11pH and Solubility
Unit 8 key ideas
pH of strong and weak species
Strong acids and bases ionise completely, so pH comes straight from concentration. Weak acids need Ka and an equilibrium calculation; for a small Ka, [H₃O⁺] ≈ √(Ka × C).
Buffers resist pH change
A buffer contains a weak acid and its conjugate base. Added acid reacts with the base and added base reacts with the acid. Henderson–Hasselbalch: pH = pKa + log([A⁻]/[HA]).
Titration curves
At the half-equivalence point pH = pKa. At equivalence, a weak acid titrated with a strong base gives a basic solution because the conjugate base remains.
Structure and strength
Acids are stronger when their conjugate base is more stable, for example when more electronegative atoms or extra oxygen atoms spread the negative charge.
Common Unit 8 mistakes
- Treating a weak acid as fully ionised.
- Assuming the equivalence point is always pH 7.
- Swapping [A⁻] and [HA] in the Henderson–Hasselbalch equation.
How to study this unit
- Before calculating, decide whether the solution is a strong acid/base, a weak acid/base or a buffer, then pick the method.
- Sketch a titration curve and label the buffer region, half-equivalence point and equivalence point.
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More AP Chemistry practice tests
- Unit 1 · 7–9%Atomic Structure and Properties
- Unit 2 · 7–9%Compound Structure and Properties
- Unit 3 · 18–22%Properties of Substances and Mixtures
- Unit 4 · 7–9%Chemical Reactions
- Unit 5 · 7–9%Kinetics
- Unit 6 · 7–9%Thermochemistry
- Unit 7 · 7–9%Equilibrium
- Unit 8 · 11–15%Acids and Bases
- Unit 9 · 7–9%Thermodynamics and Electrochemistry
About these questions
StudyCoach wrote these questions for this test. Each one is mapped to a topic in the College Board's current AP Chemistry course framework. Every answer key was also checked by a separate AI review, and any disagreement was rechecked by hand. They have not yet been reviewed by an AP Chemistry teacher. If you think an answer is wrong, email support@studycoach.io.
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