A classmate says, "Atomic theory is only a theory, so nobody has tested it." Which reply uses the word theory as scientists do?Wikipedia, Scientific theory (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0002 (history and nature of science).
A student times how long an antacid tablet takes to dissolve in water at 10 °C, 25 °C and 40 °C, using the same volume of water each time. Which is the independent variable?Wikipedia, Dependent and independent variables (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0001 (scientific inquiry).
The accepted density of a metal is 8.96 g/cm³. A student's four trials give 7.41, 7.40, 7.42 and 7.41 g/cm³. How should the results be described?Wikipedia, Accuracy and precision (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0001 (scientific inquiry).
By the rules for significant figures, how should the sum 12.11 g + 18.0 g + 1.013 g be reported?Purdue University Division of Chemical Education, General Chemistry Topic Review, Significant Figures (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0001 (scientific inquiry).
Show all 51 questions (47 more)
I. Nature of science, continued
CFCs are stable in the lower atmosphere. Why do they thin the ozone layer once they reach the stratosphere?U.S. Environmental Protection Agency, Basic Ozone Layer Science (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0003 (science, technology, engineering, mathematics and society).
The Haber process (also known as the Haber–Bosch process) is industry's main source of which compound, in demand for nitrogen fertilizers?Wikipedia, Haber process (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0003 (science, technology, engineering, mathematics and society).
Which choice applies the green chemistry principle that EPA calls atom economy?U.S. Environmental Protection Agency, Basics of Green Chemistry (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0003 (science, technology, engineering, mathematics and society).
Which principle, confirmed by Antoine Lavoisier in the late eighteenth century, marked the passage from alchemy to modern chemistry?Wikipedia, Conservation of mass (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0002 (history and nature of science).
Why did Dmitri Mendeleev's 1869 periodic table win over other chemists?Wikipedia, Dmitri Mendeleev (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0002 (history and nature of science).
II. Matter and atomic structure 9
A 50 g piece and a 500 g piece are cut from the same bar of pure copper. Which property is the same for both pieces?Wikipedia, Intensive and extensive properties (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0004 (properties of matter).
A gas occupies 6.0 L at 100 kPa. With temperature and amount of gas held constant, what volume does it occupy at 300 kPa?NASA Glenn Research Center, Boyle's Law (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0006 (kinetic molecular theory, phase changes and the gas laws).
A sealed balloon holds 2.0 L of gas at 300 K. At constant pressure it is warmed to 360 K. What is its new volume?NASA Glenn Research Center, Charles and Gay-Lussac's Law (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0006 (kinetic molecular theory, phase changes and the gas laws).
Brass is made by melting copper and zinc together in proportions that can vary. How is brass classified?Wikipedia, Alloy (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0004 (properties of matter).
Chlorine has atomic number 17. One of its atoms has 20 neutrons. What is the mass number of that atom?U.S. Department of Energy, DOE Explains...Isotopes (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0005 (atomic theory and the periodic table).
Frost on a windshield disappears on a dry, sunny day when the temperature never rises above freezing. Which phase change explains it?U.S. Geological Survey Water Science School, Sublimation and the Water Cycle (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0006 (kinetic molecular theory, phase changes and the gas laws).
How does first ionization energy generally change across a row of the periodic table from left to right, and down a column?Purdue University Division of Chemical Education, General Chemistry Topic Review, Ionization Energy and Electron Affinity (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0005 (atomic theory and the periodic table).
Phosphorus has atomic number 15. What is its ground-state electron configuration?Los Alamos National Laboratory, Periodic Table of Elements, Phosphorus (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0005 (atomic theory and the periodic table).
Simple distillation separates the components of a liquid mixture by using a difference in which property?Wikipedia, Distillation (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0004 (properties of matter).
III. Energy and chemical bonding 12
A 25.0 g piece of metal gives off 585 J of heat as it cools from 85.0 °C to 25.0 °C. What is the specific heat of the metal?U.S. Geological Survey Water Science School, Specific Heat Capacity and Water (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0007 (thermodynamics and calorimetry).
A reaction releases heat (ΔH < 0) and increases entropy (ΔS > 0). At constant temperature and pressure, when is it spontaneous?Wikipedia, Gibbs free energy (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0007 (thermodynamics and calorimetry).
Boron trifluoride, BF₃, has three bonding pairs and no lone pairs on boron. Which shape and F–B–F angle does VSEPR theory predict?Purdue University Division of Chemical Education, Valence-Shell Electron-Pair Repulsion Theory (VSEPR) (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0010 (chemical bonding and intermolecular forces).
Butane and isobutane both have the molecular formula C₄H₁₀, but their atoms are connected in different orders. What are they?Wikipedia, Structural isomer (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0009 (nomenclature and structure of compounds).
On an energy diagram for a reaction, what does adding a catalyst change?U.S. Department of Energy, DOE Explains...Catalysts (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0008 (energy in bonding, reactions and physical processes).
Step 1, A → B, has ΔH = −110 kJ. Step 2, B → C, has ΔH = −283 kJ. By Hess's law, what is ΔH for A → C?Wikipedia, Hess's law (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0007 (thermodynamics and calorimetry).
Sweat cools the skin as it evaporates. What is the reason?U.S. Geological Survey Water Science School, Evaporation and the Water Cycle (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0008 (energy in bonding, reactions and physical processes).
Using bond energies of 436 kJ/mol for H–H, 243 kJ/mol for Cl–Cl and 431 kJ/mol for H–Cl, estimate ΔH for H₂ + Cl₂ → 2 HCl.Wikipedia, Bond-dissociation energy (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0008 (energy in bonding, reactions and physical processes).
Water boils at 100 °C, while hydrogen sulfide, a heavier molecule of the same shape, boils far below 0 °C. What accounts for the difference?Wikipedia, Hydrogen bond (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0010 (chemical bonding and intermolecular forces).
What is the formula of iron(III) oxide?Purdue University Division of Chemical Education, General Chemistry Topic Review, Common Polyatomic Ions and Naming Compounds (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0009 (nomenclature and structure of compounds).
Which molecular formula fits an open-chain alkene with exactly one carbon–carbon double bond?Wikipedia, Alkene (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0009 (nomenclature and structure of compounds).
Why do solid metals conduct electricity well?Wikipedia, Metallic bonding (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0010 (chemical bonding and intermolecular forces).
IV. Chemical reactions 12
A solution has a hydrogen ion concentration of 1.0 × 10⁻⁵ M. What is its pH, and is the solution acidic or basic?Wikipedia, pH (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0013 (acid-base chemistry).
For 2 SO₂(g) + O₂(g) ⇌ 2 SO₃(g), which expression is the equilibrium constant Kc?Wikipedia, Equilibrium constant (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0012 (chemical equilibrium).
In a galvanic (voltaic) cell, where does oxidation take place, and which way do electrons travel through the wire?Wikipedia, Galvanic cell (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0014 (oxidation-reduction and electrochemistry).
In a titration, 18.0 mL of 0.150 M NaOH exactly neutralizes 30.0 mL of HCl. What concentration does the acid have?Purdue University Division of Chemical Education, General Chemistry Topic Review, Solutions (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0013 (acid-base chemistry).
In the forward reaction NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, which species acts as the Brønsted–Lowry acid?Wikipedia, Brønsted–Lowry acid–base theory (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0013 (acid-base chemistry).
In the reaction Zn + Cu²⁺ → Zn²⁺ + Cu, which species is oxidized?Wikipedia, Redox (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0014 (oxidation-reduction and electrochemistry).
N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g) is at equilibrium. The volume of the container is reduced, raising the pressure. What happens?Wikipedia, Le Chatelier's principle (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0012 (chemical equilibrium).
What is the oxidation number of chromium in the dichromate ion, Cr₂O₇²⁻?Purdue University Division of Chemical Education, General Chemistry Topic Review, Oxidation Numbers (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0014 (oxidation-reduction and electrochemistry).
What is true of a reversible reaction once it has reached chemical equilibrium?Wikipedia, Chemical equilibrium (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0012 (chemical equilibrium).
When C₅H₁₂ + O₂ → CO₂ + H₂O is balanced with the smallest whole numbers, what is the coefficient of O₂?Purdue University Division of Chemical Education, General Chemistry Topic Review, Chemical Equations (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0011 (nature of chemical reactions).
Why does warming a reaction mixture usually increase the rate of reaction?Wikipedia, Collision theory (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0011 (nature of chemical reactions).
Zn + 2 HCl → ZnCl₂ + H₂ is an example of which type of reaction?Wikipedia, Single displacement reaction (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0011 (nature of chemical reactions).
V. Stoichiometry and solutions 9
A flashlight beam shows as a bright path through fog or diluted milk, but not through salt water. What does the visible beam show?Wikipedia, Tyndall effect (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0017 (solutions and colloidal suspensions).
Aqueous solutions of glucose, NaCl and CaCl₂ are made at the same molality. Assuming the salts dissociate completely, which freezes at the lowest temperature?Wikipedia, Colligative properties (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0017 (solutions and colloidal suspensions).
For 2 Mg + O₂ → 2 MgO, how many grams of MgO form when 4.86 g of Mg burns in excess oxygen? Use 24.3 g/mol for Mg and 40.3 g/mol for MgO.Purdue University Division of Chemical Education, General Chemistry Topic Review, Chemical Equations (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0016 (stoichiometry).
For N₂ + 3 H₂ → 2 NH₃, a vessel holds 2.0 mol N₂ and 3.0 mol H₂. Which reactant is limiting, and how much NH₃ can form?Wikipedia, Limiting reagent (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0016 (stoichiometry).
The molar mass of carbon dioxide is 44.01 g/mol. How many moles are in 22.0 g of CO₂?National Institute of Standards and Technology, NIST Chemistry WebBook, Carbon dioxide (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0015 (the mole concept).
The theoretical yield of a synthesis is 25.0 g. A student isolates 20.0 g of product. What is the percent yield?Wikipedia, Yield (chemistry) (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0016 (stoichiometry).
Using an Avogadro constant of 6.022 × 10²³ per mole, how many molecules are in 0.250 mol of carbon dioxide?National Institute of Standards and Technology, CODATA Value: Avogadro constant (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0015 (the mole concept).
What is the percent by mass of hydrogen in water? Use 1.008 g/mol for H and 18.02 g/mol for H₂O.National Institute of Standards and Technology, NIST Chemistry WebBook, Water (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0015 (the mole concept).
What volume of 6.0 M HCl must be diluted to prepare 300 mL of 1.0 M HCl?Purdue University Division of Chemical Education, General Chemistry Topic Review, Solutions (read 2026-10-09). Outline: NES Chemistry (306) framework, competency 0017 (solutions and colloidal suspensions).
How this list was compiled: Our own questions, written to the 17 competencies of the NES Chemistry test (306) as its test framework prints them on the National Evaluation Series site of Pearson (https://www.nestest.com/static/docs/NES_Framework_306.pdf and https://www.nestest.com/test/306, read 2026-10-09): Nature of Science, competencies 0001-0003, 18%; Matter and Atomic Structure, 0004-0006, 18%; Energy and Chemical Bonding, 0007-0010, 23%; Chemical Reactions, 0011-0014, 23%; Stoichiometry and Solutions, 0015-0017, 18%. This bank holds three questions for each competency: 9, 9, 12, 12 and 9. Every fact was read on 2026-10-09 in the public page named under its question (NIST, NASA Glenn, USGS, EPA, the Department of Energy, Los Alamos National Laboratory, Purdue University and Wikipedia), and every worked answer was recomputed. Licence: Questions, choices and explanations are original work of this site.
How it works
This free NES Chemistry practice test has 51 questions of our own, three for each competency of test 306, about a third of them worked problems. It is unofficial and not affiliated with Pearson, which owns the National Evaluation Series.
Read the full guide
NES Chemistry study guide: the five domains
By the framework read October 9, 2026, test 306 weights Nature of Science 18%, Matter and Atomic Structure 18%, Energy and Chemical Bonding 23%, Chemical Reactions 23%, and Stoichiometry and Solutions 18%.
How the 51 questions are spread
Nine, nine, twelve, twelve and nine. Exam mode asks 50 in 75 minutes, the real pace of 150 questions in 3 hours and 45 minutes.
Where the answers come from
Each explanation names its public page: NIST, NASA Glenn, the USGS Water Science School, EPA, the Department of Energy, Los Alamos, Purdue's general chemistry review or the named Wikipedia article. Worked answers show the arithmetic.
The real test supplies an on-screen calculator, a sheet of constants and a periodic table, so practice with a periodic table open.
Write the unit beside every number. Many wrong choices here come from one slip, such as dividing where you should multiply.
Questions and answers
Is this free NES Chemistry practice test the real exam?
No. The 51 questions are our own, each written to one competency of the 306 framework and checked at the public page its explanation names. No real question, sample question or item of the paid practice test was used.
How many questions are on the NES Chemistry test?
Test 306 has 150 multiple-choice questions and 3 hours and 45 minutes of testing time. Counting the 15-minute tutorial and the nondisclosure agreement, the appointment is 4 hours.
What is the passing score for NES Chemistry?
The test page shows a national benchmark of 220 and links the passing scores of Arizona, Washington and Wisconsin, as each state may set its own. A practice result here is a count of right answers, not a scaled score.
Is NES Chemistry 321 the same test as 306?
No. Test 321 follows a May 2023 framework with three domains and has 100 multiple-choice questions, while 306 has five domains and 150. Both are on the NES list, so check with your state's licensing agency which one it requires.