High school chemistry practice test: 8 free questions with worked answers

The daily High School Chemistry paper has 8 original questions worth 25 to 35 marks. It covers atomic structure and isotopes, bonding, moles and reacting masses, concentration and titration, energy changes, rates, equilibrium, chemical analysis, electrolysis and organic chemistry. Electrolysis and organic chemistry go further than many first-year courses, so check your syllabus.

Free chemistry practice test: 8 questions

We wrote these questions for this page. Give yourself 30 minutes with a calculator and a periodic table. Use H = 1.0 and O = 16 for molar masses.

1. How many protons, neutrons and electrons are in an atom of chlorine-37? (Chlorine's atomic number is 17.)
2. Boron is 19.9% boron-10 and 80.1% boron-11. Calculate its average atomic mass.
3. How many moles of water are in 36 g, and how many molecules is that?
4. Balance: Al + O₂ → Al₂O₃
5. Hydrogen burns: 2H₂ + O₂ → 2H₂O. What mass of water forms from 4.0 g of hydrogen?
6. 25.0 mL of 0.100 M NaOH is exactly neutralized by 20.0 mL of HCl. What is the concentration of the HCl?
7. Use collision theory to explain why a reaction speeds up when it is heated.
8. What is the pH of a 0.010 M solution of hydrochloric acid?

Chemistry practice test answers

1. 17 protons, 20 neutrons, 17 electrons. The atomic number tells you the protons, and with no overall charge the electrons match them. Neutrons = mass number − atomic number = 37 − 17 = 20. Build it in the Atom Builder.

2. 10.8. Weight each isotope by how common it is: 10 × 0.199 + 11 × 0.801 = 1.99 + 8.811 = 10.8. The answer sits nearer 11 because boron-11 is far more common. Try one from our Atomic Structure course, then press Mark.

3. 2.0 mol, or 1.2 × 10²⁴ molecules. Water's molar mass is 2(1.0) + 16 = 18 g/mol, so 36 ÷ 18 = 2.0 mol. Multiply by Avogadro's number: 2.0 × 6.02 × 10²³ = 1.2 × 10²⁴ molecules. The Moles Calculator checks conversions like this.

4. 4Al + 3O₂ → 2Al₂O₃. Oxygen comes in pairs on the left and threes on the right, so make 6 oxygen atoms on each side: 3O₂ and 2Al₂O₃. That gives 4 aluminum atoms on the right, so put 4 in front of Al. Check with the Equation Balancer.

5. 36 g. 4.0 g of H₂ at 2.0 g/mol is 2.0 mol. The equation gives 2 mol of water for every 2 mol of hydrogen, so 2.0 mol of water forms, which is 2.0 × 18 = 36 g. Always go through moles: grams of one substance never convert straight to grams of another.

6. 0.125 M. Moles of NaOH = 0.100 × 0.0250 L = 0.00250 mol. NaOH and HCl react 1 to 1, so there is 0.00250 mol of HCl in 0.0200 L, and 0.00250 ÷ 0.0200 = 0.125 M. Remember to change mL to L. Practice with the Titration Lab.

7. At a higher temperature the particles move faster, so they collide more often. More importantly, a larger share of collisions have at least the activation energy, so more of them lead to a reaction. A full answer gives both reasons.

8. pH 2. HCl is a strong acid, so it ionizes fully and [H⁺] = 0.010 M. Then pH = −log(0.010) = 2. Each step of 1 on the pH scale is a factor of 10 in [H⁺]. The pH Calculator works these out.

Chemistry Regents and other state tests

Whether you sit an end-of-course chemistry exam depends on your state. New York has two Regents exams in chemistry. Past papers for the newer Physical Science: Chemistry (NYSP12SLS) exam start in June 2026. The August 2026 paper ran on Wednesday, August 19, from 8:30 to 11:30 a.m., and students needed a scientific or graphing calculator and the 2025 Edition Reference Tables for Physical Science: Chemistry. NYSED also keeps past papers for the older Physical Setting/Chemistry exam. Each comes with a scoring key, rating guide and conversion chart.

Use the daily paper as a short timed practice test

1. Open today's High School Chemistry paper with a periodic table, and work to the suggested time, 30 to 35 minutes.
2. Show every mole step and keep units in each line.
3. Mark it with the mark scheme and note the topic behind each lost mark.
4. Fill gaps with the Atomic Structure, Chemical Bonding and Reaction Kinetics courses.

Common chemistry mistakes

• Changing subscripts to balance an equation: change only the numbers in front.
• Skipping the mole ratio in stoichiometry.
• Leaving volumes in mL when using molarity.
• Confusing mass number and atomic number.
• Giving only one reason for a rate change when collision theory has two.

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