Free CLEP Chemistry Practice Questions

Sample Practice Questions

Try these 10 sample questions from the CLEP Chemistry practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A neutral atom has atomic number 17 and mass number 37. How many neutrons does it contain?

   1. A.17
   2. B.20Correct answer: B
   3. C.37
   4. D.54

   Explanation: OpenStax states: "The total number of protons and neutrons in an atom is called its mass number (A)." Subtract the 17 protons from 37 nucleons to obtain 20 neutrons.

   Reference: Chemistry 2e, Atomic Structure and Symbolism — Atomic Structure and Symbolism, Atomic Number and Mass Number

2. 2An ideal gas is compressed from 4.0 L to 2.0 L at constant temperature and fixed amount. Its initial pressure is 1.0 atm. What is its final pressure?

   1. A.0.50 atm
   2. B.1.0 atm
   3. C.2.0 atmCorrect answer: C
   4. D.4.0 atm

   Explanation: Boyle’s law states, "The volume of a given amount of gas held at constant temperature is inversely proportional to the pressure under which it is measured." Halving volume doubles pressure from 1.0 atm to 2.0 atm.

   Reference: Chemistry 2e, The Ideal Gas Law — Boyle’s Law

3. 3In HCl + H₂O → H₃O⁺ + Cl⁻, which species acts as the Brønsted–Lowry acid?

   1. A.Hydrogen chloride, HClCorrect answer: A
   2. B.Water, H2O
   3. C.Hydronium, H3O+
   4. D.Chloride, Cl−

   Explanation: OpenStax states, "A compound that donates a proton to another compound is called a Brønsted-Lowry acid". HCl donates H⁺ to water in the forward reaction.

   Reference: Chemistry 2e, Brønsted-Lowry Acids and Bases — Section 14.1, Brønsted-Lowry Acids and Bases

4. 4When aqueous CaCl₂ and AgNO₃ react to form AgCl(s), which ions are spectators?

   1. A.Ca²⁺ and NO₃⁻Correct answer: A
   2. B.Ag⁺ and Cl⁻
   3. C.Ca²⁺ and Cl⁻
   4. D.Ag⁺ and NO₃⁻

   Explanation: OpenStax notes, "These spectator ions—ions whose presence is required to maintain charge neutrality—are neither chemically nor physically changed by the process". Calcium and nitrate appear unchanged on both sides of the complete ionic equation.

   Reference: Chemistry 2e, Writing and Balancing Chemical Equations — Section 4.1, Ionic and Molecular Equations

5. 5What is true of a reversible reaction at dynamic equilibrium?

   1. A.Forward and reverse rates are equalCorrect answer: A
   2. B.Both reaction rates are zero
   3. C.Reactant and product concentrations are equal
   4. D.The forward reaction alone continues

   Explanation: OpenStax says, "a reaction at equilibrium has not “stopped,” but is proceeding in the forward and reverse directions at the same rate." The two reactions continue at equal rates even if concentrations differ.

   Reference: Chemistry 2e, Chemical Equilibria — Section 13.1, Chemical Equilibria

6. 6At fixed temperature, doubling [A] while keeping other concentrations constant makes the initial rate four times as large. What is the order in A?

   1. A.Zero
   2. B.First
   3. C.SecondCorrect answer: C
   4. D.Third

   Explanation: OpenStax states, "The reaction orders in a rate law describe the mathematical dependence of the rate on reactant concentrations." A fourfold rate change for a twofold concentration change means 2ⁿ = 4 and n = 2.

   Reference: Chemistry 2e, Rate Laws — Section 12.3, Rate Laws

7. 7A system reaches the same final state from the same initial state by two different paths. Which statement about a state function is correct?

   1. A.Its change is the same for both pathsCorrect answer: A
   2. B.Its change depends on the path length
   3. C.Its value depends on the rate of each path
   4. D.Its change must be zero for both paths

   Explanation: OpenStax states, "The value of a state function depends only on the state that a system is in, and not on how that state is reached." Equal initial and final states give equal changes.

   Reference: Chemistry 2e, Enthalpy — Enthalpy, State Functions

8. 8What principal products form when sodium metal reacts with water?

   1. A.Hydrogen gas and sodium hydroxideCorrect answer: A
   2. B.Hydrogen gas and sodium oxide
   3. C.Oxygen gas and sodium hydroxide
   4. D.Oxygen gas and sodium oxide

   Explanation: OpenStax states, "The alkali metals all react vigorously with water to form hydrogen gas and a basic solution of the metal hydroxide." Sodium is an alkali metal, so the reaction produces hydrogen and sodium hydroxide.

   Reference: Chemistry 2e, Periodicity — Group 1: The Alkali Metals

9. 9In a glass graduated cylinder, an aqueous liquid forms a concave meniscus. At eye level, its lowest point reads 25.6 mL and its upper edge reads 25.8 mL. What volume should be recorded?

   1. A.25.6 mLCorrect answer: A
   2. B.25.7 mL
   3. C.25.8 mL
   4. D.26.0 mL

   Explanation: OpenStax states, "To measure the volume of liquid in a graduated cylinder, you should make a reading at the bottom of the meniscus". The bottom reads 25.6 mL.

   Reference: Chemistry 2e, Measurement Uncertainty, Accuracy, and Precision — Significant Figures in Measurement

10. 10Two neutral atoms are isotopes of the same element. Which quantity can differ between the atoms?

    1. A.Their number of protons
    2. B.Their number of neutronsCorrect answer: B
    3. C.Their number of electrons
    4. D.Their atomic number

    Explanation: OpenStax describes magnesium isotopes: "All magnesium atoms have 12 protons in their nucleus. They differ only because a 24Mg atom has 12 neutrons in its nucleus, a 25Mg atom has 13 neutrons, and a 26Mg has 14 neutrons." Isotopes share the same proton count and atomic number but can have different neutron counts.

    Reference: Chemistry 2e, Atomic Structure and Symbolism — Section 2.3, Atomic Structure and Symbolism