CLEP Chemistry Practice 2026 practice questions and answers. Tap an option to test yourself — you'll see the correct answer and a plain-English explanation for every question. Free, no login.
Q21What is the atomic mass of Carbon-12?
✓ Correct answer: D. 12.000 amu
Answer: 12.000 amu The atomic mass of Carbon-12 is defined as exactly 12.000 atomic mass units (amu). This standard is used as a reference in atomic mass measurements, making it important for understanding the scale and calculation of atomic masses in chemistry.
Q22Water is composed of hydrogen and oxygen (formula $$H_2O$$). What type(s) of bonds do you expect to find in the water molecule?
✓ Correct answer: C. Covalent only
Answer: Covalent only Even without having a table of electronegativities, you can accurately predict that since both hydrogen and oxygen are non-metals, they likely form covalent bonds. Remember that ionic bonds generally occur between metals and non-metals, where the difference in electronegativity is such that the non-metal steals electrons from the metal instead of sharing the electrons between atoms.
Q23Consider the ionic radius of a chlorine atom (Cl) compared to its cation (Cl⁺) and its anion (Cl⁻). How do they compare?
✓ Correct answer: D. Cl > Cl⁺; Cl < Cl⁻
If a chlorine atom loses an electron to become a cation ($$Cl^+$$), its radius shrinks because it has lost its outer-most electron. Conversely, if it gains an electron to become an anion ($$Cl^-$$), its radius increases due to the added electron and the associated repulsive effects.
Q24Which element will likely form stronger covalent bonds: C (electron configuration $$1s^2 2s^2 2p^2$$) or Si (electron configuration $$1s^2 2s^2 2p^6 3s^2 3p^2$$)?
✓ Correct answer: E. C, because it has a smaller atomic radius and can form stronger bond overlaps
Answer: C, because it has a smaller atomic radius and can form stronger bond overlaps. Covalent bonding strength is influenced by the ability of atoms to effectively overlap their bonding orbitals. Carbon's smaller atomic radius allows for a more effective orbital overlap, resulting in stronger bonds compared to silicon.
Q25Which of the following diagrams properly illustrates the Rutherford atomic model?
✓ Correct answer: B. Electrons in random motion around a dense nucleus
Answer: Electrons in random motion around a dense nucleus In the Rutherford model, the atom consists of a small, dense nucleus surrounded by electrons that move in a random fashion. Rutherford's experiment with alpha particles showed that atoms are mostly empty space with a tiny, dense, positively charged nucleus.
Q26Which of the following properties can be determined by studying the kinetics of a reaction that cannot be inferred from its balanced chemical equation? i. Activation energy ii. Reaction intermediates iii. Reaction rate iv. Product yield
✓ Correct answer: C. i., ii., and iii.
Answer: i., ii., and iii. The balanced chemical equation provides information about stoichiometry and the overall products and reactants. However, it does not indicate the activation energy, reaction intermediates, or rate of the reaction. Kinetics studies reveal the activation energy needed to start the reaction, identify intermediate species formed during the reaction, and measure the speed (reaction rate). The yield of products, however, is typically determined by the extent of the reaction and thermodynamics, not kinetics.
Q27Consider the reaction step involving $$2X + Y \rightarrow $$ products. What is the molecularity of this reaction step?
✓ Correct answer: E. Termolecular
A reaction step involving three molecules (2X and Y) coming together is termed termolecular. The molecularity of a reaction step is the number of molecules that must collide simultaneously for the reaction to occur. In this case, since the step involves three molecules, it is termed termolecular.
Q28Consider a reaction system with various components: solids, solvents, dissolved ions, and gases. When writing the equilibrium constant expression for this system, which of the following should be included? Component Solids Solvents Dissolved ions (concentration) Gases
✓ Correct answer: B. Dissolved ions (concentration) and Gases
By definition, pure solids and pure solvents are excluded from equilibrium constant expressions. Only the concentrations of dissolved ions and the partial pressures of gases are included.
Q29What does a very small equilibrium constant, $$K$$, indicate about a chemical reaction?
✓ Correct answer: D. The reaction essentially does not occur at all
Answer: The reaction essentially does not occur at all The equilibrium constant $$K$$ is a ratio of the concentration of products to reactants. A very small $$K$$ value indicates that there are many more reactants than products at equilibrium, suggesting that the reaction hardly proceeds forward.
Q30Identify the spectator ion(s) in the following reaction: $$Na_2SO_4$$ $$(aq) + BaCl_2$$ $$(aq) \rightarrow BaSO_4$$ $$(s) + 2 NaCl$$ $$(aq)$$
✓ Correct answer: A. $$Na^+, Cl^-$$
The correct answer is $$Na^+, Cl^-$$. A spectator ion is present in solution but does not participate in the reaction. It is helpful to look for ions that remain aqueous throughout the reaction. In this case, $$Na^+, Cl^-$$ remain dissolved in solution, while $$Ba^{2+}$$ and $$SO_4^{2-}$$ react to form a precipitate.
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