20 CLEP Chemistry practice questions, with answers and video walkthroughs

Twenty practice questions for CLEP Chemistry, in the real exam's style. Score 16 of 20 here and you are in passing range. Miss more than four, and the pattern of your misses points straight at the topic to review next. Every question below is explained on video, including why the wrong answers trap most test-takers.

What students preparing for this exam tell us is that steady practice in the exam's format, with an explanation for every miss, is what moves a score. Use these the same way: answer, check, and read why the wrong choices are tempting. For the full plan around them, see the CLEP Chemistry pillar guide.

Watch the full video walkthrough above, then test yourself on the twenty questions below. Each one is explained on the video, including why the wrong answers trap most test-takers.

Questions 1 to 5 (questions 1 to 5)

1. What part of the atom determines which element it is? Protons. An element is defined by its number of protons, its atomic number. Change the protons and you change the element. Change the neutrons and you only get a different isotope of the same element.

2. Atoms of the same element always share the same number of protons but can differ in their number of: Neutrons. Atoms of one element that differ in neutron count are called isotopes. Carbon twelve and carbon fourteen are both carbon, six protons each, but carbon fourteen carries two extra neutrons.

3. As you move from left to right across a period of the periodic table, atomic radius generally: Decreases. Across a period, protons are added to the nucleus while electrons fill the same energy level. The stronger nuclear pull draws the electrons in tighter, so atoms get smaller from left to right.

4. The chemical properties of an element are determined mainly by: Its Valence Electrons. It is the outermost electrons, the valence electrons, that take part in bonding. That is why elements in the same column, with the same number of valence electrons, behave alike.

5. Which group of elements is the most chemically unreactive? The Noble Gases. The noble gases in the far right column have full valence shells, so they have little tendency to gain, lose, or share electrons. That full shell is why they almost never react.

Questions 6 to 10 (questions 6 to 10)

6. A chemical bond formed by the transfer of electrons from a metal to a nonmetal is called: An Ionic Bond. When a metal gives up electrons to a nonmetal, the two form oppositely charged ions that attract each other. That electron transfer is an ionic bond, the kind that holds table salt together.

7. In a covalent bond, the bonding atoms: Share Electrons. Covalent bonds form between nonmetals that share pairs of electrons. In a water molecule, oxygen shares electrons with two hydrogen atoms rather than taking them outright.

8. A water molecule is polar mainly because: Oxygen Pulls the Shared Electrons More Strongly Than Hydrogen. Oxygen is far more electronegative than hydrogen, so it pulls the shared electrons toward itself. That uneven sharing gives the molecule a negative end and a positive end, which makes it polar.

9. The three-dimensional shape of a molecule is determined mainly by: The Repulsion Between Electron Pairs Around the Central Atom. Electron pairs around a central atom repel one another and spread out as far apart as possible. That spacing sets the molecule's shape, the idea behind the valence shell electron pair repulsion model.

10. Water has an unusually high boiling point for such a small molecule because of: Hydrogen Bonding. Water molecules attract one another through hydrogen bonds, an unusually strong intermolecular force. Breaking those extra attractions takes more energy, which pushes the boiling point higher.

Questions 11 to 15 (questions 11 to 15)

11. At constant temperature, if you decrease the volume of a gas, its pressure will: Increase. This is Boyle's law: pressure and volume are inversely related at constant temperature. Squeeze a gas into a smaller space and its molecules strike the walls more often, so the pressure rises.

12. According to Charles's law, heating a gas at constant pressure causes its volume to: Increase. Charles's law ties volume and temperature directly together. As a gas gets hotter its molecules move faster and push outward, so the volume expands when pressure is held constant.

13. The process in which a solid turns directly into a gas, without first becoming a liquid, is called: Sublimation. Sublimation is the direct solid to gas change. Dry ice, which is frozen carbon dioxide, sublimes at room temperature, turning straight into gas with no puddle in between.

14. In a solution of salt water, the salt is the: Solute. The substance present in the smaller amount, the one being dissolved, is the solute. The water doing the dissolving is the solvent. So in salt water, salt is the solute and water is the solvent.

15. For most solid solutes, raising the temperature of the water will: Increase How Much Can Dissolve. Most solids dissolve more readily in hot water than cold, which is why more sugar dissolves in hot tea. Gases do the opposite: they become less soluble as the temperature climbs.

Questions 16 to 20 (questions 16 to 20)

16. A balanced chemical equation must show the same number of each kind of atom on both sides because of the law of: Conservation of Mass. Matter is neither created nor destroyed in a chemical reaction, so every atom that goes in must come back out. That is the law of conservation of mass, and it is why equations must be balanced.

17. On the pH scale, a solution with a pH of 2 is: Strongly Acidic. The pH scale runs from zero to fourteen. Seven is neutral, lower numbers are acidic, higher numbers are basic. A pH of two sits well below seven, so it is strongly acidic, near the level of lemon juice.

18. When an acid reacts with a base, the two products are usually a salt and: Water. Acid base neutralization produces a salt plus water. The acid's hydrogen ion and the base's hydroxide ion combine to form water, while the remaining ions pair up to form the salt.

19. In an oxidation reduction reaction, the substance that loses electrons is said to be: Oxidized. Losing electrons is oxidation and gaining electrons is reduction. A common memory aid is oil rig: oxidation is loss, reduction is gain. So the substance that loses electrons is the one being oxidized.

20. If you add more reactant to a system at equilibrium, the reaction will shift to: Produce More Product. Le Chatelier's principle says a system at equilibrium responds to a stress by shifting to relieve it. Add more reactant and the balance shifts toward the product side to use up the excess.

What to do with your score

The point of twenty questions is not the twenty, it is the pattern. Mark which topic each miss came from, then spend your next session on that topic alone. None of it requires starting over, only tightening the spots that cost you points.

A single twenty-question set is a snapshot, not a study plan. To pass with margin you need volume: enough questions, in the exam's format, with explanations that turn a wrong answer into a correction. That is what Flying Prep's CLEP Chemistry practice is built for: every question explained, with a free trial before you decide.