• 52 questions

AP Chemistry Gas Laws Practice Test

Unofficial multiple-choice practice on gases for AP Chemistry: the ideal gas law, partial pressures, kinetic molecular theory and real gases.

Which equation is the ideal gas law?

Pick an answer, then press Check answer. Then you see Correct or Not quite, with the reason. Keys: A to D pick, Enter checks.

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Unofficial practice questions, not affiliated with the College Board. Bank checked October 10, 2026.

Next step Next unit: AP Chemistry Unit 4Chemistry questions on every topic

All 52 questions

Topic 3.4: Ideal gas law, PV = nRT 20

  • A 2.00 g sample of a gas occupies 1.12 L at 273 K and 1.00 atm. What is its molar mass? (R = 0.08206 L·atm/(mol·K)) Wikipedia, "Ideal gas law"; course topic 3.4
  • A gas at 2.0 atm fills 3.0 L. It expands to 12 L at constant temperature. What is the new pressure? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • A gas occupies 4.0 L at 1.0 atm and 200 K. What volume does it occupy at 2.0 atm and 400 K? Wikipedia, "Ideal gas law"; course topic 3.4
  • A rigid tank holds gas at 1.50 atm and 300 K. The tank is heated to 450 K. What is the new pressure? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • A sealed 8.21 L cylinder at 400 K shows a pressure of 2.00 atm. How many moles of ideal gas does it hold? (R = 0.08206 L·atm/(mol·K)) Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • A weather balloon holds 3.0 L of helium at 27 °C. The sun warms it to 77 °C with no change in pressure. What is its new volume? Wikipedia, "Charles's law"; course topic 3.4
Show all 52 questions (46 more)

Topic 3.4: Ideal gas law, PV = nRT, continued

  • At constant temperature and pressure, the number of moles of gas in a balloon is doubled. What happens to its volume? Wikipedia, "Avogadro's law"; course topic 3.4
  • For a fixed amount of ideal gas at constant pressure, what does a graph of volume against Kelvin temperature look like? Wikipedia, "Charles's law" and AP Chemistry Course and Exam Description, essential knowledge 3.4.A.3; course topic 3.4
  • For a fixed amount of ideal gas at constant temperature, what does a graph of pressure against volume look like? Wikipedia, "Boyle's law" and AP Chemistry Course and Exam Description, essential knowledge 3.4.A.3; course topic 3.4
  • In PV = nRT, in which unit must the temperature be expressed? Wikipedia, "Ideal gas law"; course topic 3.4
  • Two identical rigid flasks are at the same temperature. Flask A holds 2.0 g of H₂ (2.0 g/mol), and flask B holds 2.0 g of He (4.0 g/mol). How do the pressures compare? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • The volume of a gas is plotted against temperature in degrees Celsius at constant pressure, and the straight line is extended back to zero volume. At about what temperature does it reach zero? Wikipedia, "Charles's law"; course topic 3.4
  • The volume of a sealed sample of gas is halved while its Kelvin temperature is doubled. By what factor does the pressure change? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • What is the density of nitrogen gas, N₂ (28.0 g/mol), at 2.00 atm and 300 K? (R = 0.08206 L·atm/(mol·K)) Wikipedia, "Ideal gas law"; course topic 3.4
  • What is the pressure of 0.250 mol of an ideal gas in a 5.00 L flask at 300 K? (R = 0.08206 L·atm/(mol·K)) Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • What mass of carbon dioxide, CO₂ (44.0 g/mol), fills a 5.00 L flask at 1.00 atm and 300 K? (R = 0.08206 L·atm/(mol·K)) Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • What volume does 1.00 mol of an ideal gas occupy at 273 K and 1.00 atm? (R = 0.08206 L·atm/(mol·K)) Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • Which change doubles the pressure of a fixed amount of gas in a rigid container? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • Which equation is the ideal gas law? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • Which of these gases has the greatest density at the same temperature and pressure? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.4

Topic 3.4: Partial pressures and mole fraction 10

  • A 2.0 L flask of helium at 3.0 atm is joined to a 4.0 L flask of neon at 1.5 atm, and the gases mix at constant temperature. What is the total pressure? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • A flask holds equal masses of helium (4.0 g/mol) and methane (16 g/mol). Which gas has the larger partial pressure? AP Chemistry Course and Exam Description, essential knowledge 3.4.A.2; course topic 3.4
  • A mixture contains 3.0 mol of N₂ and 1.0 mol of O₂. What is the mole fraction of O₂? AP Chemistry Course and Exam Description, essential knowledge 3.4.A.2; course topic 3.4
  • A mixture of 2.0 mol of He and 6.0 mol of Ne has a total pressure of 4.0 atm. What is the partial pressure of helium? AP Chemistry Course and Exam Description, essential knowledge 3.4.A.2; course topic 3.4
  • A rigid flask holds nitrogen. Argon is pumped in at constant temperature. What happens to the partial pressure of the nitrogen? AP Chemistry Course and Exam Description, essential knowledge 3.4.A.2; course topic 3.4
  • Carbon dioxide (0.40 mol), nitrogen (0.60 mol) and argon (1.00 mol) are sealed together at a total pressure of 2.0 atm. How much of that pressure is due to the nitrogen? AP Chemistry Course and Exam Description, essential knowledge 3.4.A.2; course topic 3.4
  • Hydrogen is collected over water at a total pressure of 760 torr. At that temperature the vapor pressure of water is 24 torr. What is the partial pressure of the hydrogen? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • Three gases share a flask: nitrogen contributes 0.50 atm, oxygen 0.30 atm and argon 0.20 atm. What does a pressure gauge on the flask read? Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • What is the partial pressure of a gas in a mixture? Wikipedia, "Partial pressure" and Purdue University, General Chemistry Topic Review, "Gas Laws"; course topic 3.4
  • What is the sum of the mole fractions of all the gases in a mixture? Wikipedia, "Mole fraction"; course topic 3.4

Topic 3.5: Kinetic molecular theory 14

  • A gas in a rigid container is heated. In terms of particles, why does the pressure rise? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • A gas is squeezed to half its volume at constant temperature, and its pressure doubles. What is the particle-level reason? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • A sample of nitrogen gas is held at 300 K. What is true of the speeds of its molecules? AP Chemistry Course and Exam Description, essential knowledge 3.5.A.1; course topic 3.5
  • According to the kinetic molecular theory, what causes the pressure of a gas? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • How does the kinetic molecular theory treat the volume of the gas particles themselves? Wikipedia, "Kinetic theory of gases"; course topic 3.5
  • In the kinetic molecular theory, collisions are perfectly elastic. What does that mean? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • The Kelvin temperature of a gas is doubled. What happens to its particles' average kinetic energy? AP Chemistry Course and Exam Description, essential knowledge 3.5.A.3; course topic 3.5
  • The Kelvin temperature of a gas is raised to four times its starting value. By what factor does the typical speed of its particles change? Wikipedia, "Maxwell–Boltzmann distribution"; course topic 3.5
  • Maxwell–Boltzmann curves of molecular speed are drawn for helium and for argon at the same temperature. How do they compare? Wikipedia, "Maxwell–Boltzmann distribution" and Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • Maxwell–Boltzmann curves of molecular speed are drawn for one gas at 300 K and at 600 K. How does the 600 K curve differ? Wikipedia, "Maxwell–Boltzmann distribution"; course topic 3.5
  • More gas is pumped into a rigid tank at constant temperature. Why does the pressure rise? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • Samples of helium and xenon are at the same temperature. How do the average kinetic energies of their atoms compare? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • Samples of helium and xenon are at the same temperature. Which atoms move faster on average? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5
  • Which statement is a postulate of the kinetic molecular theory of gases? Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.5

Topic 3.6: Deviation from ideal gas law 8

  • A gas is cooled until it is close to condensing. Which cause of non-ideal behavior matters most under these conditions? AP Chemistry Course and Exam Description, essential knowledge 3.6.A.1; course topic 3.6
  • At very high pressure a real gas takes up more volume than the ideal gas law predicts. What causes this? Purdue University, General Chemistry Topic Review, "Deviations from the Ideal Gas Law"; course topic 3.6
  • Helium has the lowest boiling point of any element, about 4 K. What does that show about its atoms? Wikipedia, "Helium" and Purdue University, General Chemistry Topic Review, "Deviations from the Ideal Gas Law"; course topic 3.6
  • The measured pressure of a real gas is sometimes lower than the ideal gas law predicts. What causes this? Purdue University, General Chemistry Topic Review, "Deviations from the Ideal Gas Law"; course topic 3.6
  • Real gases condense to liquids when they are cooled enough. Why would an ideal gas never condense? Purdue University, General Chemistry Topic Review, "Deviations from the Ideal Gas Law"; course topic 3.6
  • Under which conditions do real gases deviate most from ideal behavior? Purdue University, General Chemistry Topic Review, "Deviations from the Ideal Gas Law"; course topic 3.6
  • Which sample of nitrogen behaves most like an ideal gas? Wikipedia, "Ideal gas"; course topic 3.6
  • Which two assumptions of the kinetic molecular theory break down for real gases? Purdue University, General Chemistry Topic Review, "Deviations from the Ideal Gas Law" and Purdue University, General Chemistry Topic Review, "Kinetic Molecular Theory"; course topic 3.6

How this list was compiled: Our own questions, written to the gas topics of Unit 3 (Properties of Substances and Mixtures) in the College Board's AP Chemistry Course and Exam Description, effective fall 2024, https://apcentral.collegeboard.org/media/pdf/ap-chemistry-course-and-exam-description.pdf, read 2026-10-10: topic 3.4 Ideal Gas Law, topic 3.5 Kinetic Molecular Theory and topic 3.6 Deviation from Ideal Gas Law. Each rule was read on 2026-10-10 in the public page named under its question: the General Chemistry Topic Review of Purdue University, a Wikipedia article or an essential knowledge statement of the course description. Every calculated answer is worked from the numbers the question prints and was worked out a second time on 2026-10-10. Licence: Own work. Short quotations from the public documents named under each question.

How it works

This AP Chemistry gas laws practice test has 52 questions of our own on the gases of Unit 3, from PV = nRT to real gases. It is unofficial and not affiliated with or endorsed by the College Board.

Read the full guide

Where gases sit in the course

In the College Board's course description, read October 10, 2026, gases are three of the thirteen topics of Unit 3: 3.4 Ideal Gas Law (30 questions here, 10 of them on partial pressures), 3.5 Kinetic Molecular Theory (14) and 3.6 Deviation from Ideal Gas Law (8). The description gives topics no weights, so the spread is ours.

Constants and sources

A question prints the gas constant when it needs it, R = 0.08206 L·atm/(mol·K), the value on the exam's equation sheet. Rules were read in a Purdue University chemistry review, a Wikipedia article or the description, named under each answer.

  • Change Celsius to kelvins before any gas calculation: K = °C + 273.
  • Partial pressure follows moles. The pressure of one gas is its mole fraction times the total pressure.
  • Real gases stray at low temperature and high pressure: attractions lower the pressure, and particle volume raises the volume.

Questions and answers

What unit are gas laws in AP Chemistry?

Unit 3, Properties of Substances and Mixtures, in topics 3.4 to 3.6. The whole unit is 18 to 22% of the multiple-choice section, by the College Board's course page, and also covers intermolecular forces and solutions.

Is the ideal gas law on the AP Chem exam?

Yes. Topic 3.4 is PV = nRT with partial pressures and mole fraction. Boyle's and Charles's laws are not named in the description; they are the same equation with two of the four variables held constant.

Do you have to memorize R for the AP Chemistry exam?

No. The equations and constants sheet printed in the course description gives the gas constant as 8.314 J/(mol·K) and 0.08206 L·atm/(mol·K). Pick the value whose units match your pressure and volume.

When does a real gas deviate from the ideal gas law?

Near the conditions where it would condense, when attractions between particles matter, and at extremely high pressure, when the volume of the particles themselves matters. That is the whole of topic 3.6.

Are these real AP Chemistry gas law questions?

No. The College Board owns the real questions, and none appears here, even in other words. Every question was written for this page from the three gas topics the course description lists.

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