Not sure how to begin studying for the AP Chemistry exam? This review guide will help you figure out what's on the test and how you can ace it. I'll go over the exam structure, provide sample questions in each format, list the concepts you can expect to see on the test, and give you some tips on how to get the most out of your studying. I just looked into my PrepScholar Crystal Ball™ and saw a 5 in your future, so get ready to kick this test's butt.
What’s the Format of the AP Chemistry Exam?
The AP Chemistry exam is 3 hours and 15 minutes long and has two sections: multiple-choice (90 minutes long) and free-response (105 minutes long). There are 60 multiple-choice questions and seven free-response questions. The free-response section contains three long response (worth 10 points each) and four short response (worth four points each) questions. You're allowed to use a calculator on the free response section, but you can't use one for multiple-choice.
Time management is important on the AP Chemistry exam because you can easily get caught up in difficult problems. Try not to spend more than a minute on each multiple-choice question during your first pass through the section so that you don’t miss any questions at the end that you could have answered. You’ll have time to go back and revisit the ones you skipped if you pace yourself. For the free-response questions, you should limit your time to around 5-10 minutes for short response questions and 15-20 minutes for long response questions.
What Do AP Chemistry Questions Look Like?
The following are examples of official AP Chemistry questions in multiple-choice, short response, and long response format. I’ll go over the answers in detail to give you a sense of the types of problems you’ll face on the test and how you might solve them.
Multiple-Choice Sample Question
Multiple-choice AP Chemistry questions are often chunked together. In other words, several questions will pertain to a single experiment or dataset. Here’s an example:
In this case, you’re asked why a certain outcome resulted from an experiment. You need to know why the pressure in the container would increase based on the changes that occurred. A and B suggest that the increase in pressure has to do with intermolecular attractions either decreasing or increasing in the flask. These choices are incorrect because the intermolecular attractions between these molecules wouldn’t be significant enough to make a difference in the pressure of the container.
For Choice C, the first part is correct: the number of molecules has increased with the decomposition of PCl5. It also makes sense that this would result in a higher frequency of collisions with the walls of the container. This answer is looking pretty good.
Choice D is wrong because there’s no reason to expect that the molecules have increased in speed inside the container during the reaction.
Since we ruled out all the other options, Choice C is the correct answer!
Short Response Sample Question
For part A, you needed to draw out the interactions between the ions and water molecules in the solution. Three points were awarded for:
- A representation of at least one Li+ ion and one Cl- ion clearly separated and labeled correctly
- Each ion surrounded by at least two water molecules
- Water molecules must be oriented correctly (oxygen end is closer to the lithium ion, and hydrogen end is closer to the chloride ion)
Part b was worth one point for identifying the chemical species and providing justification. The species produced at the cathode would be H2(g) and OH-(aq) (you could say either one of these for the point). The hydrogen atoms in water are reduced to H2 at the cathode because this reaction has a lower magnitude reduction potential than that of the reduction of lithium ions to Li (-0.83 vs. -3.05).
Long Response Sample Question
Here’s an example of a long free-response question from the 2015 exam:
This question expects a lot from you. There’s stoichiometry, chemical bonds, intermolecular forces, Lewis diagrams, and thermodynamics! It’s testing whether you can apply a bunch of disparate skills that you’ve learned throughout the year to the scenario presented on the test.
Let’s look at part a:
For part i of part a, we need to calculate the number of moles of ethene that are produced in the experiment and measured in the gas collection tube. The first step is to calculate the pressure of the ethene so that we can use the ideal gas law to figure out the number of moles of gas produced. We can find the pressure of the water by using the given figure for water’s vapor pressure at 305 K: 35.7 torr. Since 1 atm = 760 torr, we can convert the vapor pressure to atm like so:
35.7 torr x (1 atm/760 torr) = 0.047 atm
Then, we can find the vapor pressure of the ethene by subtracting that number from the total vapor pressure of the gas produced:
0.822 atm (total vapor pressure) - 0.047 atm (water’s vapor pressure) = 0.775 atm (ethene’s vapor pressure)
Finally, we can use the ideal gas law to figure out how many moles of ethene were produced:
PV = nRT
n = PV/RT
n = (0.775 atm)(0.0854 L)/(0.08206 L atm mol-1 K-1)(305 K)
n = 0.00264 moles of ethene produced
Ok, now let’s move onto part ii of part a.
How many moles of ethene would be produced if the dehydration reaction went to completion? To solve this problem, we need to reference the total amount of ethanol originally put into the tube, 0.2 grams, as well as the molar mass of ethanol. Using these numbers, we can see how many moles of ethanol were put into the tube:
0.2 grams ethanol x (1 mole ethanol / 46.1 grams) = 0.00434 moles of ethanol
Ok, that’s the number of moles of ethanol that were put in, but we’re trying to find the number of moles of ethene that would result if the reaction went to completion. Since both molecules have coefficients of 1 in the equation, they exist in a one to one mole ratio. This means that the answer is 0.00434 moles of ethene.
Now for part b!
The percent yield of ethene in the experiment is pretty easy to find based on our answers to part a. We know that the amount of ethene that was actually produced was 0.00264 moles. The amount that would have been produced if the reaction went to completion was 0.00434 moles. To find the percent yield, we can just divide 0.00264 by 0.00434 and multiply the answer by 100:
0.00264 mol / 0.00434 mol x 100 = 60.8 percent yield
In part c, you are asked to agree or disagree with the student's claim that the reaction at 298 K has an equilibrium constant of less than 1 and provide justification in the form of calculations for△G°298. According to the formula sheet:
△G° = △H° - T△S°
△G° = 45.5 kJ/mol - (298 K)(0.126 kJ/ K*mol)
△G° = 8.0 kJ/mol
Referencing our formulas again, the equilibrium constant, Kp, is equal to e(-△G°/RT). Since we found that △G° was greater than 0, Kp has to be e raised to some negative number, resulting in a solution equal to a number less than 1. The student is correct that Kp must be less than 1 at 298 K.
Part d asks you to complete a Lewis electron-dot diagram. Your answer would look like this:
The diagram should include all the bonding pairs, plus two non-bonding pairs on the O atom.
In part e, you're asked to determine the C-O-H bond angle. This molecule is tetrahedral around the oxygen atom. That means that the bond angle is approximately 109.5 degrees. On this question, you got a point for any answer between 100 and 115 degrees. Technically, the bond angle would be a little smaller because of the two unbonded electron pairs on the oxygen atom. For visual reference:
In part f, you have to explain why ethene was collected as a gas after the experiment and ethanol was not. This happened because ethene isn’t as soluble as ethanol in water. Ethene is only slightly water-soluble because the weak dipole intermolecular attractions between nonpolar ethene molecules and polar water molecules are weaker than the hydrogen bonds between water molecules. Ethanol molecules are water soluble because they're polar, so they form hydrogen bonds with water molecules as they dissolve.
These bears are like ethanol and ethene. The one on the left is ethanol because it's CLEARLY more polar.
Again, notice how many different skills we used in this one question. We had to know how to:
- Calculate the number of moles of a gas that were produced by a reaction given the temperature, vapor pressure and volume (with vapor pressure calculated indirectly)
- Calculate the number of moles of a gas produced by a reaction taken to completion given the mass of the reactant
- Calculate percent yield of a reaction
- Calculate the equilibrium constant of a reaction at a given temperature
- Draw Lewis electron dot diagrams
- Determine bond angles
- Explain how polarity and intermolecular attraction would impact the outcome of a reaction and the states of its products
You only have a short amount of time for each free-response question (around 20 minutes for the long ones and 10 for the short ones), so you need to have all the information you learned in the course pretty well-mastered if you want to earn the majority of these points!
What Topics Does AP Chemistry Cover?
The AP Chemistry course is structured around six main themes or “Big Ideas.” These Big Ideas encompass smaller, more specific themes that the College Board calls “Enduring Understandings.” I’ll list the Big Ideas and their corresponding Enduring Understandings in this section. I’ll also provide a more straightforward lists of relevant topics under each Big Idea with links to some notes.
Big Idea 1: The chemical elements are fundamental building materials of matter, and all matter can be understood in terms of arrangement of atoms. These atoms retain their identities in chemical reactions.
- Enduring Understanding 1.A: All matter is made of atoms. There are a limited number of types of atoms; these are the elements.
- EU 1.B: The atoms of each element have unique structures arising from interactions between electrons and nuclei.
- EU 1.C: Elements display periodicity in their properties when the elements are organized according to increasing atomic number. Periodicity is a useful principle for understanding properties and predicting trends in properties.
- EU 1.D: Atoms are so small that they are difficult to study directly; atomic models are constructed to explain experimental data on collections of atoms.
- EU 1.E: Atoms are conserved in physical and chemical processes.
- Chemical Foundations
- Scientific method
- Significant figures
- Basics of systematic problem-solving
- Organization/classification of matter
- Atomic structure and periodicity
- Atoms, Molecules, and Ions
- Dalton’s atomic theory
- Millikan’s oil experiment
- Rutherford’s metal foil experiment
- Timeline of milestones in the history of chemistry
- Atomic structure
- Types of bonds
- Chemical formulas for molecules
- Organization of the periodic table
- Naming compounds
Big Idea 2: Chemical and physical properties of materials can be explained by the structure and arrangement of atoms, ions, or molecules and the forces between them.
- EU 2.A: Matter can be described by its physical properties. The physical properties of a substance generally depend on the spacing between the particles (atoms, molecules, ions) that make up the substance and the forces of attraction among them.
- EU 2.B: Forces of attraction between particles (including the noble gases and also different parts of some large molecules) are important in determining many macroscopic properties of a substance, including how the observable physical state changes with temperature.
- EU 2.C: The strong electrostatic forces of attraction holding atoms together in a unit are called chemical bonds.
- EU 2.D: The type of bonding in the solid state can be deduced from the properties of the solid state.
- Types of chemical bonds
- Bond polarity and dipole moments
- Ions: size and electron configuration
- London dispersion forces
- Lewis structures
- VSEPR Model
- Covalent Bonding: Orbitals
- Liquids and Solids
- Intermolecular forces
- The liquid state
- Structures and types of solids
- Structure and bonding in metals
- Vapor pressure and state changes
- Phase diagrams
- Gas laws of Boyle, Charles, and Avogadro
- Ideal gas law
- Gas stoichiometry
- Dalton’s law
- Kinetic Molecular Theory
- van der Waal’s equation
- Atmospheric chemistry
- Gas law practice problems
Big Idea 3: Changes in matter involve the rearrangement and/or reorganization of atoms and/or the transfer of electrons.
- EU 3.A: Chemical changes are represented by a balanced chemical equation that identifies the ratios with which reactants react and products form.
- EU 3.B: Chemical reactions can be classified by considering what the reactants are, what the products are, or how they change from one into the other. Classes of chemical reactions include synthesis, decomposition, acid-base, and oxidation-reduction reactions.
- EU 3.C: Chemical and physical transformations may be observed in several ways and typically involve a change in energy.
- Atomic and molar mass
- Percent composition of compounds and determining formulas for compounds
- Structure of chemical equations
- Balancing chemical equations
- Limiting reactant problems
- Percent yield
- Types of Chemical Reactions and Solution Chemistry
Big Idea 4: Rates of chemical reactions are determined by details of the molecular collisions.
- EU 4.A: Reaction rates that depend on temperature and other environmental factors are determined by measuring changes in concentrations of reactants or products over time.
- EU 4.B: Elementary reactions are mediated by collisions between molecules. Only collisions having sufficient energy and proper relative orientation of reactants lead to products.
- EU 4.C: Many reactions proceed via a series of elementary reactions.
- EU 4.D: Reaction rates may be increased by the presence of a catalyst.
Big Idea 5: The laws of thermodynamics describe the essential role of energy and explain and predict the direction of changes in matter.
- EU 5.A: Two systems with different temperatures that are in thermal contact will exchange energy. The quantity of thermal energy transferred from one system to another.
- EU 5.B: Energy is neither created nor destroyed, but only transformed from one form to another.
- EU 5.C: Breaking bonds requires energy, and making bonds releases energy.
- EU 5.D: Electrostatic forces exist between molecules as well as between atoms or ions, and breaking the resultant intermolecular attractions requires energy.
- EU 5.E: Chemical or physical processes are driven by a decrease in enthalpy or an increase in entropy, or both.
- Chemical Equilibrium
- Equilibrium conditions
- Equilibrium constants
- Solving equilibrium problems
- Le Chatelier’s principle
- All about energy
- Enthalpy and calorimetry
- Hess’s Law
- Spontaneity, Entropy, and Free Energy
- Gibbs Free energy (G)
- Entropy changes in chemical reactions
- Free energy and chemical reactions
- Free energy
- ...and pressure
- ...and equilibrium
- ...and work
- The Nucleus
- Nuclear stability and radioactive decay
- Kinetics of radioactive decay
- Nuclear transformations
- Thermodynamic stability of the nucleus
- Nuclear fission and fusion
Big Idea 6: Any bond or intermolecular attraction that can be formed can be broken. These two processes are in a dynamic competition, sensitive to initial conditions and external perturbations.
- EU 6.A: Chemical equilibrium is a dynamic, reversible state in which rates of opposing processes are equal.
- EU 6.B: Systems at equilibrium are responsive to external perturbations, with the response leading to a change in the composition of the system.
- EU 6.C: Chemical equilibrium plays an important role in acid-base chemistry and in solubility.
- EU 6.D: The equilibrium constant is related to temperature and the difference in Gibbs free energy between reactants and products.
- Properties of Solutions
- Solution composition
- Factors affecting solubility
- Vapor pressure of solutions
- Boiling point and freezing point variation
- Osmotic pressure
- Solubility and complex ion equilibria
- Solubility and solubility products
- Common Ion effects
- Acids and Bases
- The pH scale
- Calculating pH
- Acid-base properties of salts and oxides
- Calculating acid strength
- Lewis Acid-Base Model
- Solving acid-base problems
- Acid-Base equilibria
- Buffered solutions
- Acid-base indicators
Tips for AP Chemistry Review
Tip #1: Start From the Beginning
Get your fundamentals straight before you try to do more complicated problems. On many AP Chemistry questions, you have to integrate a few pieces of essential knowledge and apply them to a given scenario. If you’re shaky on the foundational concept, you won’t be able to get to the correct answer. When you start studying, fill the gaps in your knowledge from earlier in the course first.
Tip #2: Redo Problems You Didn’t Get the First Time
If you can’t figure out a problem and have to look up the solution, don’t just read over what you were supposed to do and leave it at that. Review the steps you should have taken to get the correct answer, and then, without looking at them, try to resolve the problem.
Learning by doing is very important in chemistry. Make sure you know why you’re solving the problem a certain way. You should also reinforce your knowledge by going through other similar problems.
Tip #3: Do Lots of Free-Response Questions
You might be tempted to stick with practicing multiple-choice questions because you can do a lot of them quickly and feel like you’ve made significant progress. However, it’s extremely important not to ignore the free-response section of the test in your studying if you want to do well. Free-response questions are a bigger challenge to your chemistry knowledge because you have to come up with the answers independently. Practicing them will help you do better on the test as a whole. If you can answer free-response questions correctly on a consistent basis, that means you really know your stuff!
This is what's gonna happen if you don't practice free-response questions!
How to Review for AP Chemistry
Your AP Chemistry review should revolve around detecting your areas of weakness and practicing relevant problems. Here are the steps you might go through:
Step 1: Take and Score a Practice Test
The first thing you should do is take a full practice test to assess how well you know the material. It’s more efficient just to study the concepts that you’re still shaky on rather than going back through all your notes for the course. Make sure you take the test with the same time constraints as the real exam, and don’t use a calculator on the multiple-choice questions.
You should also circle any questions where you feel even a little unsure of the correct answer. You need to go over those concepts even if you end up getting the question right so you can be as comfortable as possible with all the content. When you’re done with the test, you can score it and set a goal for how much you want to improve.
Step 2: Categorize Your Mistakes (and Any Other Questions That You Were Unsure About)
Now that you’ve scored your test, go through your mistakes and lucky guesses, and sort them by topic area. This is the best way to get a clear picture of where you have the most significant issues with the content. Your list of mistakes will inform the rest of your review. I’d also recommend redoing problems that you missed to see if you can get to the correct answer.
Step 3: Review Relevant Content
If there was any essential background information on the test that you forgot, start by reviewing that content. The information that you learned in the first couple months of the course serves as a foundation for the rest of the class. After you feel confident with the basics, you can move onto studying higher-level topics. You might review your notes on how to solve certain types of problems or look back at the information in your textbook. You can also use an AP review book to study. Sometimes this is a better option because review books are specifically tailored to the test.
Step 4: Do Practice Problems
Reviewing content isn’t enough in chemistry. You need to know how to apply your knowledge to unfamiliar experimental scenarios on the test. Spend some time doing practice problems that pertain to each of your areas of weakness until you feel more comfortable with the subject matter.
Step 5: Take Another Practice Test to See If You’ve Improved
After you finish doing practice problems, try out your new skills on another practice test. You can score the new test and see whether you’re satisfied with your new (and hopefully improved) scores. You always have the option of repeating this process if there’s still room for growth. If you don’t see much improvement, you may have to go back and reevaluate your study methods.
If there are some concepts that you’re having a really hard time wrapping your head around, I’d encourage you to ask your teacher or one of your classmates to help you understand the material better. Sometimes, if you can’t figure something out yourself, an alternative explanation is what you need for it to click.
Here’s an approximate time breakdown for all of these steps:
- Take and score a practice test: 4 hours
- Categorize your mistakes: 1 hour
- Review content: 2 hours
- Do practice problems: 2 hours
- Take a second practice test: 4 hours
Total time for one cycle: 13 hours
Now it's time to set off on your own personal review journey. Good luck out there. No, I don't know why someone sculpted a ceramic frog with a rolling suitcase, but I have to assume that their life is much more interesting than mine.
The AP Chemistry exam covers a challenging set of concepts that require skills in math, factual recall, and analytical thinking. It's also one of the longest AP tests, lasting three hours and 15 minutes total. To recap, the types of questions on the test include:
- 60 multiple-choice questions (90 minutes)
- Seven free-response questions (105 minutes) made up of
- Three long response (10 points each)
- Four short response (four points each)
AP Chemistry covers six main themes that encompass many more specific topics. These themes or "Big Ideas" are:
The chemical elements are fundamental building materials of matter, and all matter can be understood in terms of arrangement of atoms. These atoms retain their identities in chemical reactions.
Chemical and physical properties of materials can be explained by the structure and arrangement of atoms, ions, or molecules, and the forces between them.
Changes in matter involve the rearrangement and/or reorganization of atoms and/or the transfer of electrons.
Rates of chemical reactions are determined by details of the molecular collisions.
The laws of thermodynamics describe the essential role of energy and explain and predict the direction of changes in matter.
Any bond or intermolecular attraction that can be formed can be broken. These two processes are in a dynamic competition, sensitive to initial conditions and external perturbations.
Some study tips that I would recommend implementing as you prepare for the exam include:
- Start with the basics
- Redo problems that you miss
- Practice free-response questions regularly
When you study, you follow these steps for the best results:
- Take and score a practice test
- Categorize your mistakes
- Review content
- Do practice problems
- Take a second practice test
If you keep up with your classwork throughout the year and adhere to the advice in this article, you'll have no problem doing well on the AP test!
If you're thinking about buying a review book to supplement your in-class notes, check out my list of the best AP Chemistry review books.
Still planning out your schedule for the rest of high school? Read this guide for advice on which AP classes you should take based on your academic interests.
Are you considering taking an online AP class that your high school doesn't offer? Learn more about online AP classes and whether they're worth it for you.
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Samantha is a blog content writer for PrepScholar. Her goal is to help students adopt a less stressful view of standardized testing and other academic challenges through her articles. Samantha is also passionate about art and graduated with honors from Dartmouth College as a Studio Art major in 2014. In high school, she earned a 2400 on the SAT, 5's on all seven of her AP tests, and was named a National Merit Scholar.