AP Chemistry is hard, and it is hard in a way that is easy to describe: it is a college course taught in a school year, with calculation in nearly every unit and an exam that gives credit only for exact explanations. None of that makes it a bad choice. It makes it a course to prepare for. This page sets out what makes it hard, how it compares with the other science APs, who should take it and when, and how students score a 5.
What the pass rates show
For many years roughly half of AP Chemistry students scored 3 or above, and only about one in ten scored a 5, which put it among the harder science APs. In recent years the pass rate has risen considerably. The College Board publishes the distribution each summer; look at the latest year rather than at old reputation. Two things have stayed true throughout: the 5s go to students who practise released free-response questions, and the 1s and 2s go mostly to students who took the course without a first chemistry course underneath it.
The five things that make it hard
1. The pace. Nine units, each the size of a chapter in a college textbook, in about thirty teaching weeks. A unit missed is not recovered.
2. The maths is everywhere. Moles and stoichiometry, gas laws, molarity, equilibrium constants, pH and logarithms, thermochemistry, rate laws, electrochemistry. It is only algebra, but it is constant, and it includes logarithms, which many students meet properly for the first time here.
3. Equilibrium. Units 7 and 8, chemical equilibrium and acids and bases, are where most students fall. ICE tables, weak acids, buffers and titration curves combine new concepts with the hardest calculations in the course, and they carry a large share of the exam.
4. The free-response wording. A correct idea in loose words earns nothing. "The reaction is exothermic so it goes faster" is wrong; the rubric wants the specific cause named: particle-level explanations, the right term, the right direction. Students lose more marks here than anywhere.
5. The labs. The course requires laboratory work, and the exam asks about procedures, errors and data. A student who did the labs without understanding them has a section of the exam with nothing to say.
How it compares
| Course | Content | Maths | Memory | Where it is hardest |
|---|---|---|---|---|
| AP Chemistry | Large | Constant: algebra, logarithms | Moderate | Equilibrium; free-response wording |
| AP Physics 1 | Small | Algebra, trigonometry | Little | Reasoning in words; first physics course |
| AP Biology | Very large | Little; some statistics | Heavy | Volume; data-analysis questions |
| AP Physics C | Moderate | Calculus | Little | Content depth; the E and M course |
The question of physics against chemistry in general, with a check that predicts which you will find harder, is in is physics harder than chemistry; AP Physics 1 on its own is in is AP Physics 1 hard.
The nine units, and where students fall
| Unit | Topic | Difficulty for most |
|---|---|---|
| 1 | Atomic structure and properties | Moderate: moles begin here |
| 2 | Compound structure and properties | Moderate: bonding, Lewis structures, VSEPR |
| 3 | Properties of substances and mixtures | Moderate: intermolecular forces, gases, solutions |
| 4 | Chemical reactions | Moderate: stoichiometry, types of reaction, titration |
| 5 | Kinetics | Hard: rate laws, mechanisms |
| 6 | Thermochemistry | Moderate: enthalpy, calorimetry, Hess's law |
| 7 | Equilibrium | Hardest: K, ICE tables, Le Chatelier |
| 8 | Acids and bases | Hardest: pH, weak acids, buffers, titration curves |
| 9 | Thermodynamics and electrochemistry | Hard: entropy, free energy, cells |
Units 7 and 8 together decide most students' scores. A student who starts preparing for them in unit 4, by making stoichiometry and logarithms automatic, has a very different spring.
Should a sophomore take it?
Most schools expect a first chemistry course and Algebra 2 before AP Chemistry, which puts it in junior year. A sophomore with honors chemistry already done and strong algebra, including logarithms, can succeed. A sophomore taking chemistry for the first time usually struggles, not for lack of ability but because the course assumes the basics and moves on. If the plan is medicine, pharmacy or engineering, junior year AP Chemistry with a good score is worth more than sophomore AP Chemistry with a weak one.
The exam
Two sections of equal weight. Multiple choice, 60 questions in 90 minutes. Free response, 7 questions in 105 minutes: three long and four short, covering calculations, explanations, lab design and analysis. A periodic table and an equation sheet are provided; a calculator is allowed on the free-response section. Check the College Board's current course and exam description for any changes.
How to score a 4 or 5
- Make stoichiometry automatic early. Moles, molar mass, limiting reactant, percentage yield, molarity: ten problems a day in the first month. Every later unit sits on this.
- Learn logarithms properly before unit 8. pH, pKa and the Henderson-Hasselbalch equation are easy with logarithms and impossible without them.
- Explain at the particle level. Every "why" answer should mention particles, collisions, bonds, charges or energy, because that is what the rubric credits.
- Do released free-response questions with the scoring guidelines beside you, from the first semester. Mark your own answers. Learn the exact phrases that earn the point.
- Understand every lab, not just its result: what was measured, what could go wrong, how an error would change the answer.
- Revise by recall, not rereading. How to do that in chemistry specifically is in active recall for chemistry.
- Start equilibrium early. Preview units 7 and 8 over the winter break; they are the exam.
Where to get help
A 1-on-1 online AP Chemistry class with a tutor who holds a master's in chemistry: the maths made automatic first, each unit a week ahead of the class, and released free-response questions marked to the College Board's own scoring guidelines, with the wording corrected line by line. Also for honors chemistry and first-year college chemistry. The free 30-minute first class is a real lesson on the unit you are on.
Questions parents ask
1Is AP Chemistry hard?
2What is the AP Chemistry pass rate?
3Is AP Chemistry harder than AP Physics 1?
4Is AP Chemistry harder than AP Biology?
5Can a sophomore take AP Chemistry?
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