How to Pass the ACS Practice Exam for Gen Chem 2 in 2025
The ACS General Chemistry 2 exam is a standardized test used by many colleges to assess your understanding of second-semester general chemistry. The most direct way to prepare is to take an ACS practice exam for Gen Chem 2 under timed conditions, then review the concepts you missed.
What the ACS Gen Chem 2 Exam Actually Tests
The exam has about 70 multiple-choice questions, and you get 110 minutes to finish. That gives you roughly 90 seconds per question. The topics come from the official content outline published by the ACS Exams Institute.
The highest-weight categories are:
- Kinetics (rates of reaction, rate laws, activation energy)
- Chemical equilibrium (equilibrium constants, Le Chatelier’s principle)
- Acids and bases (pH, buffers, titrations)
- Thermodynamics (enthalpy, entropy, Gibbs free energy)
- Electrochemistry (cell potentials, Nernst equation)
A smaller portion covers solubility, coordination chemistry, and nuclear chemistry.
How to Use the Official Practice Materials
The ACS sells official practice exams and a study guide. These are the only resources that use the exact question format and difficulty level you will see on test day. When you take an ACS practice exam for Gen Chem 2, treat it like the real test. Sit in a quiet room, set a timer for 110 minutes, and do not use your notes. After you finish, score it and list every question you got wrong or guessed on. For each missed question, write down the specific concept. That list becomes your study agenda.
Study Strategy for the Five Core Topics
Kinetics and Rate Laws
Students often confuse the order of a reaction with the coefficients in the balanced equation. The rate law must be determined from experimental data, not from the stoichiometry.
Worked example: You have data showing that when the concentration of reactant A doubles, the rate quadruples. The reaction is second order with respect to A. If tripling the concentration of B has no effect on the rate, the reaction is zero order with respect to B. The overall rate law is rate = k[A]^2.
Practice problems that ask you to determine the rate constant from a graph of concentration versus time. A straight line on a plot of 1/[A] vs. time indicates a second-order reaction.
Equilibrium and Le Chatelier’s Principle
The equilibrium constant K changes only with temperature. Many questions test whether you know that adding a solid or a pure liquid does not shift the equilibrium. They also test the reaction quotient Q. If Q is less than K, the reaction proceeds forward.
Acids, Bases, and Buffers
You need to know the Henderson-Hasselbalch equation by memory. The ACS exam will not provide it.
pH = pKa + log([A-]/[HA])
A typical question gives you the concentration of a weak acid and its conjugate base, then asks for the pH after adding a small amount of strong acid. You calculate how much of the conjugate base gets neutralized, then plug the new ratio into the equation.
Thermodynamics and Gibbs Free Energy
You must know the sign conventions. A negative delta G means the reaction is spontaneous. The equation delta G = delta H – T delta S connects enthalpy, entropy, and temperature.
A common question gives you delta H and delta S at 298 K, then asks at what temperature the reaction becomes spontaneous. Set delta G to zero and solve for T. If delta H is positive and delta S is positive, the reaction becomes spontaneous at high temperature.
Electrochemistry
You need to use standard reduction potentials to calculate cell voltage. The Nernst equation (E = E° – (0.0592/n) log Q) is used for non-standard conditions. The ACS exam often tests the relationship between delta G and cell potential: delta G = –nFE.
Common Mistakes on Practice Tests
Mistake 1: Skipping unit conversions. The exam uses both kJ and J for energy. If you plug 200 J into an equation that expects kJ, your answer will be off by a factor of 1000.
Mistake 2: Forgetting to balance the half-reactions. For electrochemistry, the number of electrons transferred (n) must match the balanced redox equation.
Mistake 3: Using the wrong R value. The gas constant R appears in the Arrhenius equation, the Nernst equation, and the ideal gas law. The exam uses 8.314 J/(mol·K) for energy and 0.08206 L·atm/(mol·K) for pressure-volume work.
Mistake 4: Misreading the question. Some questions ask “which of the following is NOT true?” A student who misses the word “not” picks the correct statement and loses the point.
Final Preparation Before Test Day
Two days before the exam, take a second practice test. Compare your score to the first one. If you are still missing questions on the same topic, review that topic one more time. The night before, do not cram. Bring a non-programmable scientific calculator. You will receive a periodic table and a formula sheet with the exam, but it will not include the Henderson-Hasselbalch equation or the Nernst equation. Those you must memorize.
Key Takeaways
- The ACS Gen Chem 2 exam focuses on kinetics, equilibrium, acids/bases, thermodynamics, and electrochemistry.
- Use an official ACS practice exam for Gen Chem 2 to identify your weak areas, then study those specific topics.
- Memorize the Henderson-Hasselbalch equation, the Nernst equation, and the relationship between delta G and E.
- Watch for unit mismatches (kJ vs. J) and the word “not” in questions.
- Take a second practice test two days before the real exam to confirm your improvement.
