AP Chemistry Practice Test (2026)

In a Friday lab at West River High School, a student named Priya is asked to prepare a gold (Au) sample for an atomic-count calculation exercise. She places a small disk of 99.99% pure gold on an analytical balance and records a mass of 393.96 g. Using a copy of the periodic table at her bench (Au molar mass = 196.97 g/mol), she divides the sample mass by the molar mass and finds that her disk corresponds to exactly 2.0 mol of gold. Her lab worksheet then directs her to report the total number of individual gold atoms represented by this 2.0-mol sample, using Avogadro's number (6.022 × 10²³ particles/mol) as given in her reference sheet.

How many atoms are present in Priya's 2.0-mol sample of pure gold (Au)?

Which of the following electron configurations represents an atom in an excited state?

A crystallography research team at a fictional university lab, Ridgemoor Chemistry Institute, measures the metallic radii of four Group 1 metals using single-crystal X-ray diffraction. Each sample is sealed under argon to prevent oxidation, cooled to 180 K for measurement, and then its nearest-neighbor internuclear distance is divided by two to report a metallic radius. The team tabulates the following results, in picometers: Li = 152 pm, Na = 186 pm, K = 227 pm, Rb = 248 pm. The lab notebook asks the student operator to identify which of the four measured elements has the largest atomic radius based on these numbers and the underlying periodic trend.

Based on the data in the passage, which of the following elements has the largest atomic radius?

A mass spectrum of an unknown element shows two peaks. Peak 1 is at 62.93 amu with a relative intensity of 69.17%, and Peak 2 is at 64.93 amu with a relative intensity of 30.83%.

Based on the provided mass spectrum, which of the following elements is most likely represented?

Which of the following ions has the same number of electrons as a neutral argon atom?

A photoelectron spectrum (PES) for an element shows peaks at 104 MJ/mol, 6.84 MJ/mol, and 0.50 MJ/mol. Which of the following elements could this spectrum represent?

Which of the following statements correctly compares the first ionization energies of oxygen (O) and fluorine (F)?

The photoelectron spectrum of an unknown element is shown below. (Imagine a graph with three distinct peaks: a very high energy peak with relative intensity 2, a medium energy peak with relative intensity 2, and a low energy peak with relative intensity 6).

Based on the provided photoelectron spectrum, what is the identity of the element?

A student mixes 50.0 mL of water with 5.0 g of salt. Which of the following statements is true regarding the resulting mixture?

Which of the following sets of quantum numbers (n, l, m_l, m_s) is NOT possible for an electron in an atom?

A graph shows the first ionization energy (kJ/mol) versus atomic number for elements 1 through 20. There are drops in ionization energy at elements 3 (Li), 11 (Na), and 19 (K). There are also smaller drops at elements 5 (B), 8 (O), 13 (Al), and 16 (S).

Based on the provided graph, the drop in first ionization energy from nitrogen (N) to oxygen (O) can be best explained by which of the following?

Which of the following best describes the most common ion formed by an element with the electron configuration 1s²2s²2p⁶3s²3p⁴?

An atom of an element has three valence electrons and its outermost principal energy level is n=3. Which of the following statements about this element is true?

A student analyzes a sample of an unknown compound and determines that it contains 30.4% nitrogen and 69.6% oxygen by mass. The molar mass of the compound is experimentally determined to be approximately 92 g/mol.

What is the molecular formula of the unknown compound?

What is the molar mass of calcium carbonate, CaCO₃? (Atomic masses: Ca = 40.08 g/mol, C = 12.01 g/mol, O = 16.00 g/mol)

An element has its highest energy electron in a 4d orbital. Which of the following could be the identity of this element?

The table below shows the first four ionization energies (IE₁, IE₂, IE₃, IE₄) for an unknown element X, in kJ/mol. IE₁: 738 IE₂: 1451 IE₃: 7733 IE₄: 10540

Based on the ionization energies provided, what is the most likely identity of element X?