Second semester general chemistry has a different feel. The first semester was mostly about counting atoms and drawing molecules. The second asks why reactions go, how fast they go and how far they go before they stop. If your final is an ACS exam, you probably want a clear list of what to review before the clock starts. What’s on the ACS Gen Chem 2 exam, and how should you study each topic?
The ACS Gen Chem 2 exam usually covers intermolecular forces and solutions, chemical kinetics, chemical equilibrium, acids, bases and buffers, solubility equilibrium, thermodynamics (entropy and Gibbs free energy), electrochemistry and often nuclear chemistry. First-semester skills like stoichiometry, gas laws and Lewis structures still show up, because second-semester questions are built on top of them. The heaviest areas tend to be equilibrium and acid-base chemistry, since they connect to almost everything else. Exact coverage depends on your school’s course order and on the exam form your professor chooses. Some schools give a second-term exam, while others give a full-year exam that covers both semesters, so check your syllabus.
How Is the ACS Gen Chem 2 Exam Different From Gen Chem 1?
The biggest difference is that Gen Chem 2 is about change over time and balance, not just structure. In the first semester, most questions have a single path to the answer. In the second, you often have to decide which idea applies before you can start: Is this an equilibrium problem? A kinetics problem? A thermodynamics problem that only looks like equilibrium?
The math also gets heavier. Logarithms show up in pH and kinetics. Exponents show up in K values. Quadratics show up when shortcuts fail. None of the math is advanced, but there’s more of it per question.
And Gen Chem 1 material never leaves. A buffer problem may start with a stoichiometry step. A colligative property question needs molality, which needs molar mass. If your first-semester skills are rusty, fix those first, because they’re hiding inside second-semester questions.
Like other ACS exams, these finals are written by committees of chemistry educators through the ACS Exams Institute, are mostly multiple choice, and vary in length and time limit by form. The sample questions below are my own simple examples to show the style of thinking. They don’t come from any ACS exam.
Topics on the ACS Gen Chem 2 Exam, Part 1: Forces, Rates and Balance
Intermolecular Forces, Liquids and Solutions
Expect questions that rank boiling points, vapor pressures or solubility using London dispersion forces, dipole-dipole forces and hydrogen bonding. Colligative properties (freezing point depression, boiling point elevation, osmotic pressure) are common, and so are phase diagrams.
Try it: Which has the highest boiling point: CH4, H2S, H2O or Ne? (Answer: H2O, because of hydrogen bonding.)
How to study it: For every molecule you see, say out loud which forces it has. This turns ranking questions into a habit instead of a guess.
Chemical Kinetics
Expect rate laws, reaction order from data, integrated rate laws, half-life, activation energy and the Arrhenius equation, and reaction mechanisms. A classic trap is assuming reaction order comes from the balanced equation. It doesn’t. As OpenStax explains in its section on rate laws and reaction orders, orders are found by experiment.
Try it: Doubling [A] makes the rate four times faster. What is the order in A? (Answer: second order, since 22 = 4.)
How to study it: Practice method-of-initial-rates tables until you can spot the order in a few seconds. Keep the three integrated rate laws on one card and know which plot gives a straight line for each.
Chemical Equilibrium
Expect K expressions, Q versus K, Le Chatelier’s principle, converting between Kp and Kc, and calculating equilibrium concentrations. The calculation questions almost always run through ICE tables, so being quick and clean with them pays off across several topics.
Try it: If Q is greater than K, which way does the reaction shift? (Answer: toward reactants, to the left.)
How to study it: Do equilibrium problems in sets, and always write the K expression before touching numbers. Leave solids and pure liquids out of it.
Part 2: Acids, Solubility, Energy and Electrons
Acids, Bases and Buffers
Expect pH and pOH, strong versus weak acids and bases, Ka and Kb, conjugate pairs, salt solutions, buffers with the Henderson-Hasselbalch equation, and titration curves. This is often the biggest single block of a second-semester final.
Try it: What is the pH of 0.010 M HCl? (Answer: 2.00. HCl is a strong acid, so [H+] = 0.010 M.) And a bonus: when a buffer has equal concentrations of a weak acid and its conjugate base, what is its pH? (Answer: pH = pKa.)
How to study it: Before you calculate, classify. Strong acid, weak acid, buffer, or salt? Each one has its own method, and picking the right one is half the question.
Solubility Equilibrium
Expect Ksp expressions, molar solubility, the common ion effect and predicting whether a precipitate forms (Q versus Ksp again).
Try it: AgCl has Ksp = 1.8 × 10−10. What is its molar solubility in pure water? (Answer: about 1.3 × 10−5 M, the square root of Ksp.)
How to study it: Write the dissolving equation every time. The coefficients decide whether you get s2, 4s3 or something else.
Thermodynamics: Entropy and Gibbs Free Energy
Expect predictions about the sign of ΔS, calculations of ΔG from ΔH and ΔS, the link between ΔG° and K, and temperature-dependent spontaneity. The OpenStax chapter on free energy is a solid free review.
Try it: A reaction has ΔH < 0 and ΔS > 0. When is it spontaneous? (Answer: at all temperatures, because ΔG = ΔH − TΔS is always negative.)
How to study it: Make the four-box table of ΔH and ΔS signs and fill it in from memory until it’s automatic. Watch units, since ΔS is usually in J/K and ΔH in kJ.
Electrochemistry
Expect balancing redox reactions with half-reactions, galvanic cell diagrams, standard cell potentials, the relationship between E°, ΔG° and K, and electrolysis.
Try it: Using E° = +0.34 V for Cu2+/Cu and −0.76 V for Zn2+/Zn, what is E°cell for a zinc-copper cell? (Answer: +1.10 V, from E°cathode − E°anode.)
How to study it: Memorize “oxidation at the anode, reduction at the cathode” and never multiply E° values by coefficients.
Nuclear Chemistry
Expect balancing nuclear equations, types of decay and half-life problems. Not every course covers this, so check your syllabus.
Try it: What fraction of a radioactive sample remains after three half-lives? (Answer: 1/8, or 12.5%.)
How to study it: Balance nuclear equations by checking that mass numbers and atomic numbers both add up on each side. For half-life questions, draw a quick chain (100%, 50%, 25%, 12.5%) instead of reaching for a formula.
Which Gen Chem 1 Skills Come Back?
Almost all of them. This map shows where first-semester skills reappear, so you know what to refresh before you start reviewing new material.
| Gen Chem 1 skill | Where it shows up in Gen Chem 2 |
|---|---|
| Stoichiometry and molarity | Buffers after adding strong acid or base, titrations, electrolysis |
| Gas laws | Kp problems, kinetics of gas-phase reactions |
| Lewis structures and polarity | Intermolecular forces, acid strength |
| Enthalpy and Hess’s law | ΔG = ΔH − TΔS, temperature effects on K |
| Balancing equations | Redox half-reactions, K expressions, nuclear equations |
If one of these feels shaky, spend a short session on it before you start the matching Gen Chem 2 topic. It’s much easier to learn buffers when the stoichiometry step isn’t also a struggle.
A simple review plan works well for most students. Spend the first few sessions on equilibrium and acid-base chemistry, since they connect to solubility, electrochemistry and thermodynamics. Then rotate through the remaining topics in shorter sessions. In the last week, switch to mixed sets of problems, because the real exam won’t tell you which chapter each question came from.
Which ACS Gen Chem 2 Questions Cost the Most Points?
There’s no public, official list of most-missed questions, but three kinds of questions cause trouble for a lot of second-semester students.
- Equilibrium math. Setting up the expression, using coefficients as exponents, and knowing when the small-x shortcut is allowed.
- Buffers. Recognizing a buffer in the first place, and handling a buffer after a strong acid or base has been added (a stoichiometry step comes first).
- Thermodynamic signs. Mixing up the sign of ΔS, flipping the meaning of a negative ΔG, or forgetting to convert J to kJ.
All three share a theme. They punish students who memorized formulas without knowing when each one applies. Practice deciding what kind of problem you’re looking at, not just solving it.
Ready for the ACS Gen Chem 2 Exam?
So, what’s on the ACS Gen Chem 2 exam? Intermolecular forces and solutions, kinetics, equilibrium, acids and bases, solubility, thermodynamics, electrochemistry and often nuclear chemistry, all resting on the foundation you built in Gen Chem 1. Your school’s syllabus and exam form decide the exact mix.
Start with equilibrium and acid-base chemistry, since they feed so many other topics. Then mix problem types together the way a real final does. Our Gen Chem 2 practice exam lets you try all of these second-semester topics in the ACS multiple-choice style, and it saves your results so you can compare attempts. (ChemExams isn’t affiliated with the American Chemical Society, and the questions are our own.)
The second semester asks harder questions, but they’re the same kind of questions every time. Learn to recognize them, and the exam starts to look familiar.