A balance reads 0.05 g too high on every weighing. What kind of error does this put into a data set?Wikipedia, Observational error, Science and experiments. Written to TExES Chemistry 7–12 (240) Domain I, competency 003
A class times how long an antacid tablet takes to dissolve in water at 5 °C, 25 °C and 45 °C. What is the dependent variable?Wikipedia, Dependent and independent variables, lead section. Written to TExES Chemistry 7–12 (240) Domain I, competency 002
A prep room stores concentrated acids. Under OSHA's first aid rule, what must the work area provide where eyes or skin may be exposed to corrosive materials?OSHA, 29 CFR 1910.151, Medical services and first aid, paragraph (c). Written to TExES Chemistry 7–12 (240) Domain I, competency 001
A stoppered flask of hot water cools on the bench. Heat leaves through the glass and no matter gets in or out. Which kind of thermodynamic system is the flask?Wikipedia, Thermodynamic system, Closed system. Written to TExES Chemistry 7–12 (240) Domain I, competency 003
Show all 50 questions (46 more)
Scientific inquiry and processes, continued
A student adds measured masses of 25.1 g, 2.03 g and 0.006 g. How should the sum be reported?Purdue University, General Chemistry Topic Review, Significant Figures, Addition and Subtraction. Written to TExES Chemistry 7–12 (240) Domain I, competency 001
A student invents readings for a trial that was never run and records them in the lab notebook. Under the federal definition of research misconduct, what is this?Office of Research Integrity, Definition of Research Misconduct, paragraph (a). Written to TExES Chemistry 7–12 (240) Domain I, competency 004
A student's experiment gives 21.8 L for the volume of one mole of a gas. The accepted value under those conditions is 22.4 L. What is the percent error?Wikipedia, Approximation error, lead section. Written to TExES Chemistry 7–12 (240) Domain I, competency 001
Four titrations of one sample give 22.41, 22.43, 22.42 and 22.42 mL. The accepted value is 24.10 mL. How are these results best described?Wikipedia, Accuracy and precision, lead section. Written to TExES Chemistry 7–12 (240) Domain I, competency 001
How do the Texas chemistry TEKS describe a scientific hypothesis?Texas Essential Knowledge and Skills, 19 TAC §112.43, Chemistry, subsection (b)(3). Written to TExES Chemistry 7–12 (240) Domain I, competency 002
OSHA's laboratory standard applies where hazardous chemicals are used in a lab. Which written document must the employer develop and carry out?OSHA, 29 CFR 1910.1450, Occupational exposure to hazardous chemicals in laboratories, paragraph (e)(1). Written to TExES Chemistry 7–12 (240) Domain I, competency 001
What happens to a research paper during peer review?UC Museum of Paleontology, Understanding Science 101, Scrutinizing science: Peer review. Written to TExES Chemistry 7–12 (240) Domain I, competency 002
Whose experiments of the 1770s on the mass gained in combustion led chemists to abandon the phlogiston theory?Wikipedia, Phlogiston theory, lead section. Written to TExES Chemistry 7–12 (240) Domain I, competency 004
Matter and energy 20
A 0.10 m solution of NaCl lowers the freezing point of water about twice as far as a 0.10 m solution of glucose. Why?Wikipedia, Freezing-point depression, Calculation for dilute solution. Written to TExES Chemistry 7–12 (240) Domain II, competency 010
A 25.0 g piece of metal absorbs 235 J and warms from 20.0 °C to 40.0 °C. What is its specific heat?Purdue University, General Chemistry Topic Review, Heat, Specific Heat. Written to TExES Chemistry 7–12 (240) Domain II, competency 011
A hydrocarbon is 80.0% carbon and 20.0% hydrogen by mass. What is its empirical formula?Wikipedia, Empirical formula, lead section. Written to TExES Chemistry 7–12 (240) Domain II, competency 009
A reaction has ΔH° > 0 and ΔS° > 0. Over which temperatures is it spontaneous?Purdue University, General Chemistry Topic Review, Gibbs Free Energy, Gibbs Free Energy. Written to TExES Chemistry 7–12 (240) Domain II, competency 011
A sample of an element is 75.0% an isotope of mass 35.0 u and 25.0% an isotope of mass 37.0 u. What is its average atomic mass?Wikipedia, Standard atomic weight, lead section. Written to TExES Chemistry 7–12 (240) Domain II, competency 005
A sealed sample of gas fills 6.0 L at 300 K and 1.0 atm. What volume does it fill at 400 K and 2.0 atm?Purdue University, General Chemistry Topic Review, Gas Laws, The Ideal Gas Equation. Written to TExES Chemistry 7–12 (240) Domain II, competency 007
A solid is held together by the attraction between ions of opposite charge. Which property would you expect of it?Purdue University, General Chemistry Topic Review, Solids, Categories of Solids Based on Bonds that Hold the Solid Together. Written to TExES Chemistry 7–12 (240) Domain II, competency 008
A solution holds 10.0 g of NaOH (molar mass 40.0 g/mol) in 500 mL of solution. What is its molarity?Purdue University, General Chemistry Topic Review, Solutions, Molarity. Written to TExES Chemistry 7–12 (240) Domain II, competency 010
A tank of breathing gas for divers holds helium at a partial pressure of 3.2 atm and oxygen at a partial pressure of 0.8 atm. What is the total pressure in the tank?Purdue University, General Chemistry Topic Review, Gas Laws, Dalton's Law of Partial Pressures. Written to TExES Chemistry 7–12 (240) Domain II, competency 007
An electron in a hydrogen atom drops from n = 3 to n = 2. What does the atom do?Wikipedia, Balmer series, lead section. Written to TExES Chemistry 7–12 (240) Domain II, competency 006
Aqueous barium chloride is mixed with aqueous sodium sulfate and a white solid forms. What is the net ionic equation?Purdue University, General Chemistry Topic Review, Solubility, Solubility Rules for Ionic Compounds in Water. Written to TExES Chemistry 7–12 (240) Domain II, competency 010
For 2 H₂ + O₂ → 2 H₂O, 4.0 mol of H₂ is mixed with 3.0 mol of O₂ and reacts completely. What is the result?Purdue University, General Chemistry Topic Review, Chemical Reactions, Limiting Reagents. Written to TExES Chemistry 7–12 (240) Domain II, competency 009
Henry Moseley's X-ray measurements of 1913 gave a physical basis for ordering the periodic table by which quantity?Wikipedia, Henry Moseley, lead section. Written to TExES Chemistry 7–12 (240) Domain II, competency 005
How many moles of gas are in 4.92 L at 1.00 atm and 300 K? Use R = 0.08206 L·atm/K·mol.Texas Educator Certification Examination Program, Physical Constants for Chemistry 7–12. Written to TExES Chemistry 7–12 (240) Domain II, competency 007
Methane, CH₄, has four equal C–H bonds pointing to the corners of a tetrahedron. Which hybrid orbitals on carbon account for that shape?Purdue University, General Chemistry Topic Review, Hybrid Atomic Orbitals. Written to TExES Chemistry 7–12 (240) Domain II, competency 008
Water boils at 100 °C, yet hydrogen sulfide, a heavier molecule, is a gas at room temperature. Which force between water molecules explains the difference?Wikipedia, Hydrogen bond, Hydrogen bonds in small molecules. Written to TExES Chemistry 7–12 (240) Domain II, competency 008
What is the formula of ammonium sulfate?Purdue University, General Chemistry Topic Review, Naming Compounds, Polyatomic Ions. Written to TExES Chemistry 7–12 (240) Domain II, competency 009
Which element has the ground-state electron configuration [Ar] 3d⁶ 4s²?Wikipedia, Electron configuration, Notation. Written to TExES Chemistry 7–12 (240) Domain II, competency 006
Which of these is a chemical property of a substance, not a physical one?Wikipedia, Chemical property, Examples. Written to TExES Chemistry 7–12 (240) Domain II, competency 005
Why is the first ionization energy of potassium lower than that of sodium?Purdue University, General Chemistry Topic Review, Ionization Energy and Electron Affinity, Patterns in the First Ionization Energies. Written to TExES Chemistry 7–12 (240) Domain II, competency 006
Chemical reactions 12
A radioactive tracer has a half-life of 6 hours. What fraction of a sample is left after 24 hours?Wikipedia, Half-life, lead table. Written to TExES Chemistry 7–12 (240) Domain III, competency 015
A solution at 25 °C has [OH⁻] = 1.0 × 10⁻⁴ M. What is its pH?Purdue University, General Chemistry Topic Review, pH, pOH and Ka. Written to TExES Chemistry 7–12 (240) Domain III, competency 013
A steel pipe is coated with zinc. When the coating is scratched through, why does the bare steel still resist rusting?Wikipedia, Galvanization, Principle. Written to TExES Chemistry 7–12 (240) Domain III, competency 014
At equilibrium for N₂O₄(g) ⇌ 2 NO₂(g), [N₂O₄] = 0.10 M and [NO₂] = 0.20 M. What is K_c?Purdue University, General Chemistry Topic Review, Equilibrium Expressions, Equilibrium Constant Expressions. Written to TExES Chemistry 7–12 (240) Domain III, competency 012
For A + B → C, tripling [A] with [B] held fixed makes the initial rate nine times as large. Tripling [B] with [A] held fixed leaves the rate unchanged. What is the rate law?Purdue University, General Chemistry Topic Review, Chemical Kinetics, The Rate Law Versus the Stoichiometry of a Reaction. Written to TExES Chemistry 7–12 (240) Domain III, competency 012
Hydrogen peroxide solution is stable until a small piece of platinum is dropped in, and then it decomposes rapidly. How does the platinum act?Purdue University, General Chemistry Topic Review, Activation Energy, Catalysts and the Rates of Chemical Reactions. Written to TExES Chemistry 7–12 (240) Domain III, competency 012
In BF₃ + NH₃ → F₃B–NH₃, the boron atom accepts a pair of electrons from nitrogen. What does that make BF₃?Purdue University, General Chemistry Topic Review, Lewis Acids and Bases. Written to TExES Chemistry 7–12 (240) Domain III, competency 013
It takes 20.0 mL of 0.100 M NaOH to neutralize 25.0 mL of an HCl solution. What is the molarity of the acid?Purdue University, General Chemistry Topic Review, Solutions, Titration. Written to TExES Chemistry 7–12 (240) Domain III, competency 013
Potassium-40, atomic number 19, decays by emitting an electron (β⁻). Which nuclide is the product?Purdue University, General Chemistry Topic Review, Radioactive Decay, Beta Decay. Written to TExES Chemistry 7–12 (240) Domain III, competency 015
Standard reduction potentials are +0.34 V for Cu²⁺/Cu and −0.13 V for Pb²⁺/Pb. What is E° for the cell in which lead metal reduces Cu²⁺?Purdue University, General Chemistry Topic Review, Electrochemical Reactions, Standard-State Cell Potentials. Written to TExES Chemistry 7–12 (240) Domain III, competency 014
What is the oxidation number of nitrogen in nitric acid, HNO₃?Purdue University, General Chemistry Topic Review, Oxidation Numbers, rules 3, 7 and 9. Written to TExES Chemistry 7–12 (240) Domain III, competency 014
Why is it dangerous to mix chlorine bleach with household ammonia?Wikipedia, Sodium hypochlorite, Safety. Written to TExES Chemistry 7–12 (240) Domain III, competency 012
Science learning, instruction and assessment 6
A quiz meant to measure skill at balancing equations is written in long, dense paragraphs that weak readers cannot follow. Which quality of the quiz suffers most?Wikipedia, Test validity, lead section. Written to TExES Chemistry 7–12 (240) Domain IV, competency 017
After teaching Boyle's law, a teacher hands out both the question and the procedure for a syringe lab whose result the class already knows. Which level of inquiry is this?Wikipedia, Inquiry-based learning, Levels. Written to TExES Chemistry 7–12 (240) Domain IV, competency 016
Before a titration lab, a teacher hands out a rubric with four quality levels for the data table, the calculations and the error analysis. What does the rubric do for students?Carnegie Mellon University, Eberly Center, Creating and Using Rubrics. Written to TExES Chemistry 7–12 (240) Domain IV, competency 017
Before a unit on gases, a teacher has students predict what a sealed syringe will do in ice water and explain why. Nothing is graded. What is the main purpose?Carnegie Mellon University, Eberly Center, Assessing Prior Knowledge. Written to TExES Chemistry 7–12 (240) Domain IV, competency 016
Under the Texas Essential Knowledge and Skills, which course is a prerequisite for high school Chemistry, along with one credit of high school science?Texas Essential Knowledge and Skills, 19 TAC §112.43, Chemistry, subsection (a). Written to TExES Chemistry 7–12 (240) Domain IV, competency 016
Which of these is a summative use of assessment in a chemistry course?Carnegie Mellon University, Eberly Center, Formative vs Summative Assessment, Summative assessment. Written to TExES Chemistry 7–12 (240) Domain IV, competency 017
How this list was compiled: Our own questions, written to the exam framework of TExES Chemistry 7–12 (240) in Section 3 of the preparation manual on the Texas Educator Certification Examination Program website, https://www.tx.nesinc.com/Content/StudyGuide/TX_SG_obj_240.htm (copyright Texas Education Agency), read 2026-10-12: 100 selected-response questions in four domains, Scientific Inquiry and Processes about 24%, Matter and Energy 41%, Chemical Reactions 23%, Science Learning, Instruction and Assessment 12%. This bank holds 50 in those shares: 12, 20, 12 and 6, with every one of the 17 competencies covered. Every fact was read on the public page named under its question (47 pages, each opened 2026-10-12): Purdue University's General Chemistry Topic Review for most of the chemistry, OSHA's laboratory and first aid standards, the Physical Constants page the exam itself supplies, the Texas Essential Knowledge and Skills for Chemistry (19 TAC §112.43), the Office of Research Integrity, UC Berkeley's Understanding Science, Carnegie Mellon University's Eberly Center and Wikipedia. Fifteen answers are arithmetic from a rule the source gives. Licence: Questions, choices and explanations are original work of this site.
How it works
This online practice test for TExES Chemistry 7–12 (240) asks 50 questions of our own, weighted by the exam's four domains. It is unofficial: not affiliated with, endorsed by or sponsored by the Texas Education Agency or Pearson.
Read the full guide
What TExES Chemistry 7–12 covers
Matter and Energy is about 41% of the exam, Scientific Inquiry and Processes 24%, Chemical Reactions 23%, and Science Learning, Instruction and Assessment 12%. The 50 questions here split 20, 12, 12 and 6.
Length and timing
The exam asks 100 selected-response questions in 4 hours 45 minutes of testing, inside a 5-hour appointment. The timed exam here gives 50 questions 142 minutes, the same pace.
Where answers were checked
Most of the chemistry at Purdue University's General Chemistry Topic Review; lab safety in two OSHA standards; teaching questions at Carnegie Mellon's Eberly Center and in the Texas chemistry TEKS; the rest at Wikipedia and three other public pages.
The real exam puts a periodic table, a page of physical constants and a scientific calculator on screen.
Fifteen of the 50 questions need arithmetic: gas laws, molarity, pH, cell potentials and the like.
Questions and answers
Is there a TExES practice test for chemistry online?
Yes. This TExES practice test for chemistry runs in the browser, free and with no account. Each answer is followed by the reason and the public page it was checked on, and a question sheet prints from the page.
What should a TExES Chemistry 7-12 practice test cover?
The exam's 17 competencies, from lab safety and the nature of science to atomic structure, gases, bonding, solutions, kinetics, acids and bases, redox, nuclear reactions and science teaching. Each of the 17 has at least one question here.
What score passes TExES Chemistry 7-12?
240, by the exam's page on the program site. That is a scaled score, and the exam may carry trial questions that do not count, so the number you get right here does not convert to it.
Are these real TExES Chemistry questions?
No. Every question was written for this page from one competency of the published framework and checked on one public page. The preparation manual's sample questions were not used, and nothing is copied or reworded from the exam.