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USMLE Step 1-style Chemistry Questions
Practise chemistry (science) for the USMLE Step 1-style basic science practice: 10 multiple-choice questions, each with the correct answer and a worked explanation. Click an option to check it, or “New questions” for another set.
Chemistry practice
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Q1.The chemical formula of common salt is:
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Answer: A — NaCl
Common salt is sodium chloride.
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Q2.What is the mass of 3 mol of carbon dioxide (CO₂)? (Molar mass 44 g/mol)
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Answer: D — 132 g
Mass = moles × molar mass = 3 × 44 g/mol = 132 g.
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Q3.An oxidation reaction involves:
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Answer: A — Loss of electrons
Oxidation is loss of electrons (OIL RIG).
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Q4.What is the mass of 2.5 mol of carbon dioxide (CO₂)? (Molar mass 44 g/mol)
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Answer: A — 110 g
Mass = moles × molar mass = 2.5 × 44 g/mol = 110 g.
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Q5.Rusting of iron requires:
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Answer: B — Both oxygen and water
Iron rusts in the presence of oxygen and moisture, forming hydrated iron(III) oxide.
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Q6.What is the mass of 2 mol of methane (CH₄)? (Molar mass 16 g/mol)
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Answer: D — 32 g
Mass = moles × molar mass = 2 × 16 g/mol = 32 g.
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Q7.The periodic table is arranged in order of increasing:
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Answer: D — Atomic number
The modern periodic table orders elements by atomic number.
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Q8.What is the mass of 0.5 mol of carbon dioxide (CO₂)? (Molar mass 44 g/mol)
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Answer: A — 22 g
Mass = moles × molar mass = 0.5 × 44 g/mol = 22 g.
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Q9.The chemical name of baking soda is:
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Answer: B — Sodium bicarbonate (sodium hydrogen carbonate)
Baking soda is NaHCO₃.
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Q10.40 g of NaOH (molar mass 40) is dissolved to make 250 mL of solution. Find the molarity.
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Answer: D — 4 M
Moles = 40/40 = 1; molarity = moles ÷ litres = 1 ÷ 0.25 = 4 M.
How to approach chemistry questions
Moles = mass ÷ molar mass; molarity = moles ÷ litres. pH = −log[H⁺] and pH + pOH = 14 at 25 °C. For concepts, link each property to its position in the periodic table.
About USMLE Step 1-style
USMLE Step 1-style basic science practice — conducted by Practice in the style of the USMLE (FSMB & NBME); not affiliated. Foundational biomedical science practice for medical students preparing for licensing exams.
Original practice questions written for this site in the style and difficulty of each exam’s syllabus. They are not past papers and the site is not affiliated with any exam body. Exam patterns, marking schemes and syllabi change — always check the latest official notification.
USMLE Step 1-style practice topics
| Topic | Section | Question source |
|---|---|---|
| Biology | Science | Question bank |
| Chemistry | Science | Calculated + question bank |