Ready to give it a shot? Dive into the 10 question quiz below to get a feel for how prepared you are! Once you’ve written down your answers, hover over (or tap on a phone) the question to see the answers and explanations.
WarningPlease do keep in mind that we can’t guarantee the accuracy of this quiz, so we do recommend you also run through a full-length practice exam. The CollegeBoard offers a good one that we’ll share in the resources section below.
Question 1: Which of the following elements has the largest atomic radius?
a. Ar (atomic number 18)
b. Si (atomic number 14)
c. Cl (atomic number 17)
d. P (atomic number 15)
Why? The lowest atomic number corresponds to the fewest number of protons in the nucleus. This deficiency exerts the lowest “Effective Nuclear Charge” on the valence electrons to attract them closer to the nucleus. This result is counterintuitive—most people think that atoms get larger as the atomic number increases.
Question 2: Which of the following elements has the largest second ionization energy?
d. None of the above—they all have the same second ionization energy
Why? The second ionization of sodium requires the removal of a core electron. Core electrons require significantly more energy to remove than valence electrons. The electrons removed from Mg and Al are only valence electrons.
Question 3: Predict the precipitation product from the following displacement reaction:
Na3PO4 (aq) + CaCl2 (aq) —>
a. No reaction occurs
While both c and d represent calcium phosphate, only d has the correct ratio of these ions.
Question 4: What is the pressure exerted by 1.0 mol of an ideal gas at 25 °C in a 125 mL flask?
a. 0.0164 atm
b. 16.4 atm
c. 0.196 atm
d. 196 atm
This problem comes from the ideal gas law (PV = nRT). Temperature needs to be expressed in Kelvin, not C. Answers a and b both plug 25 °C into that expression. Volume needs to be expressed in L, not mL. Only d uses the correct units for all variables.
Question 5: How many protons does an atom of silver contain?
d. cannot determine this due to isotopic variation among silver atoms
The other answers are at least plausible as 108 represents the atomic mass of silver and 68 represents the difference between atomic number and atomic mass (the number of neutrons). There IS isotopic variation in most atoms, but that doesn’t change the atomic number (number of protons).
Question 6: Which term is used to describe the change from the solid to the gaseous state?
There are six changes in phases of matter (solid to liquid, solid to gas, liquid to gas and the reverse processes). Directly converting from solid to a gas is called sublimation (most people know this as dry ice—carbon dioxide, at –77 °C, changes from a solid to a gas without becoming a liquid—hence the term “dry” ice).
Question 7: Which of the following is the strongest Bronsted acid?
Periodic trends in the acidity of binary hydride compounds increase as you go from the top to the bottom of a group on the periodic table. The ability of the conjugate base to stabilize the negative charge that forms with the loss of the H+ ion is the key. The ions formed when all of these compounds lose a H+ get larger as you go down a group; that larger volume helps stabilize the resulting anion.
Question 8: What is the orbital hybridization of carbon atoms in a diamond? In graphite?
a. sp3, sp3
b. sp3, sp2
c. sp2, sp3
d. sp2, sp2
The structure of a diamond is an interconnected network of carbon atoms covalently bound to four other carbon atoms. To form four bonds, a carbon atom has to hybridize four atomic orbitals. In doing so, it has to hybridize the s orbital and all three p atomic orbitals (s, p, p, p = sp3). Carbon atoms in graphite bind to three other carbon atoms (and thus require only three atomic orbitals—s, p, p = sp2).
Question 9: The freezing point of helium is –270 °C. The freezing point of xenon is –112 °C. Both elements are noble gases. Which of the following statements is supported by these data?
a. Helium forms highly polar molecules
b. As the molecular weight of the noble gas increases, the freezing point decreases.
c. The London dispersion forces between helium atoms are greater than the London dispersion forces between Xenon molecules.
d. The London dispersion forces between helium atoms are less than the London dispersion forces of the Xenon molecules
Answers a and b are inane. Helium doesn’t form molecules of any type. In b, the ‘molecular’ weight is wrong. It’s ‘atomic weight’, not molecular. Either way, the freezing point doesn’t decrease anyway. Dispersion forces have everything to do with physical properties of noble gases. Xenon has significantly higher dispersion forces than helium.
Question 10: The reaction of sodium metal with water produces hydrogen gas, sodium hydroxide and heat. This process is exothermic/endothermic and the sign of the DHrxn is +/–?
Any thermochemical process that releases heat to the surroundings (as this one does) is exothermic and the calculation for the DHrxn would then be negative.
More CLEP Study Resources
Looking for a study guide to fill a couple gaps, or just want a full length practice exam? You can find a few of my favorite resources below. Note that some of the links are affiliate – meaning I’ll make a few dollars if you purchase, but I’m only sharing those resources that were genuinely helpful during my own CLEP journey.
Official CLEP Study Guide: It’s quite short on the study side of things, but this is the go-to practice test bank. I don’t think I’ve done a single CLEP test without taking the practice test in this book first.
REA CLEP Chemistry: I’m not huge on reading, but this book series is fantastic if you’re into that kind of thing. It also includes some nifty online practice tests, though I always found the official practice tests (above) more reassuring.
InstantCert Academy: The website looks like it was made before the internet, but it’s legitimately the single most useful study guide I’ve found. Basically it’s a series of flashcards that help you learn about Chemistry in a fast paced and fun way.
Plenty of other resources exist – just do a quick internet search – but these are the three that I’ve personally found the most helpful back when I did CLEP.