AP Chemistry · Exam guide
AP Chemistry FRQ Guide: Long and Short Questions, Units and Particle Explanations
The free-response half of AP Chemistry is 7 questions in 105 minutes and counts for half of your score. Three are long questions worth 10 points each, and four are short questions worth 4 points each. Nearly every question asks you to connect a calculation to a particle-level explanation, so the best preparation is practicing both halves together.
The format at a glance
| Type | How many | Points each | Typical content |
|---|---|---|---|
| Long | 3 | 10 | Several linked parts: a calculation, a lab or data set, and an explanation. Often from different units. |
| Short | 4 | 4 | One focused idea, such as a Lewis structure, a periodic trend, or a short calculation and explanation. |
| Total | 7 | 42 |
A scientific calculator is allowed on the free-response section. Show every step, with units, because graders give credit for the setup even when the final number is wrong.
What earns points
| Skill | What graders want |
|---|---|
| Setup | The formula or relationship, with values substituted in, shown in order. |
| Units and significant figures | Units carried through the work and a final answer with a sensible number of significant figures. |
| Particle-level explanation | A sentence about atoms, ions, molecules, bonds or forces, not just a restatement of the observation. |
| Claim, evidence, reasoning | A claim, the data that support it, and the chemistry that connects the two. |
A worked titration (made-up numbers)
A 25.00 mL sample of hydrochloric acid is neutralized by 20.00 mL of 0.100 M sodium hydroxide. Find the concentration of the acid.
- Moles of NaOH: 0.100 mol/L times 0.02000 L equals 0.00200 mol.
- The reaction is one to one, so HCl is also 0.00200 mol.
- Concentration of HCl: 0.00200 mol divided by 0.02500 L equals 0.0800 M.
A follow-up question might ask why the pH at the equivalence point is 7. Compare two answers.
It does not say what is in the solution or why that matters.
It names the species left in solution and ties them to the pH.
How to handle a long question
- Read the whole question first and mark which parts are calculations and which are explanations.
- Work the parts you are sure of first. Parts often stand alone, and you can skip one without losing the next.
- Carry a wrong answer forward if you need it. Graders often give credit for correct work built on an earlier mistake.
Common mistakes
- Leaving off units, or writing a unit that does not match the quantity.
- Explaining a trend with a word like "stability" instead of naming the force, such as stronger attractions between particles.
- Mixing up the moles of a substance with its concentration.
- Rounding too early, then reporting a final answer that is off in the third digit.
Frequently asked questions
How many free-response questions are on AP Chemistry?
Seven: three long questions worth 10 points each and four short questions worth 4 points each, in 105 minutes.
Can I use a calculator?
A scientific or graphing calculator is allowed on the free-response section. Show the setup either way.
Do I have to show units?
Yes. Missing or wrong units can cost points even when the number is correct.
How do I explain at the particle level?
Name the particles (ions, molecules, atoms), say what they are doing or how they attract, and tie that to the observation.
Where can I find the official scoring rules?
Exam formats change a little from year to year, so check the current course and exam description on the College Board site before test day.
Keep practicing
Every lesson in the AP Chemistry course ends with practice items and an Exam focus box, and every unit has a ten-question practice set with worked answers. These free lessons also build the skills the free-response section tests:
See the AP Chemistry course Free lessons and lesson list
Other free-response guides:
AP is a registered trademark of the College Board, which is not affiliated with and does not endorse this site. This guide is our own explanation of the question types and scoring. For the official scoring guidelines, see the College Board.