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MCAT Chemistry Questions
Practise chemistry (science) for the Medical College Admission Test: 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 hardest naturally occurring substance is:
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Answer: B — Diamond
Diamond, a carbon allotrope, is the hardest natural material.
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Q2.What is the pH of a solution with [H⁺] = 10⁻² mol/L?
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Answer: B — 2
pH = −log[H⁺] = −log(10⁻²) = 2.
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Q3.A solution with pH 3 is:
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Answer: A — Acidic
pH below 7 is acidic.
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Q4.What is the pH of a solution with [H⁺] = 10⁻⁶ mol/L?
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Answer: B — 6
pH = −log[H⁺] = −log(10⁻⁶) = 6.
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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 pH of a solution with [H⁺] = 10⁻¹ mol/L?
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Answer: B — 1
pH = −log[H⁺] = −log(10⁻¹) = 1.
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Q7.Which gas is responsible for most of the greenhouse effect from human activity?
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Answer: C — Carbon dioxide
CO₂ from burning fossil fuels is the largest human-caused contributor.
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Q8.What is the mass of 1.5 mol of calcium carbonate (CaCO₃)? (Molar mass 100 g/mol)
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Answer: D — 150 g
Mass = moles × molar mass = 1.5 × 100 g/mol = 150 g.
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Q9.Which is the most electronegative element?
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Answer: D — Fluorine
Fluorine has the highest electronegativity (3.98 on the Pauling scale).
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Q10.What is the pH of a solution with [H⁺] = 10⁻³ mol/L?
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Answer: B — 3
pH = −log[H⁺] = −log(10⁻³) = 3.
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 MCAT
Medical College Admission Test — conducted by Association of American Medical Colleges (AAMC). Medical school admission test covering biological, chemical, physical, psychological and social foundations.
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.
MCAT practice topics
| Topic | Section | Question source |
|---|---|---|
| Biology | Science | Question bank |
| Chemistry | Science | Calculated + question bank |
| Physics | Science | Calculated + question bank |