MCQ Collection
MDCAT 2026 MCQs
Practice MDCAT 2026 questions with answers and explanations.
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Correct Answer: A. A pure substance containing elements chemically combined in fixed proportions
Explanation:
Compounds have definite formulas and characteristic properties.
Their components can be separated only by chemical means.
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Correct Answer: A. Maximum product predicted from stoichiometry
Explanation:
Theoretical yield assumes complete reaction and no losses.
It is calculated from the limiting reactant.
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Correct Answer: B. A physical combination of substances with variable composition
Explanation:
Mixture components retain much of their individual identity.
They can often be separated by physical methods.
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Correct Answer: B. Amount of product experimentally obtained
Explanation:
Actual yield is measured after the experiment.
It is usually lower than theoretical yield.
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Correct Answer: C. A mixture with uniform composition throughout
Explanation:
Solutions are homogeneous mixtures.
Any sampled portion has approximately the same composition.
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Correct Answer: C. Actual yield divided by theoretical yield times 100%
Explanation:
Percent yield measures reaction and recovery efficiency.
Values below 100% commonly result from losses or incomplete reaction.
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Correct Answer: D. A mixture with nonuniform composition
Explanation:
Heterogeneous mixtures contain distinguishable regions or phases.
Examples include sand in water and granite.
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Correct Answer: D. Moles of solute per liter of solution
Explanation:
Molarity is a common concentration unit.
Its value changes with temperature because solution volume can change.
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Correct Answer: A. Melting of ice
Explanation:
A physical change alters form or state without changing chemical identity.
Ice and liquid water are both H2O.
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Correct Answer: A. Moles of solute per kilogram of solvent
Explanation:
Molality is based on solvent mass.
It is largely independent of temperature.
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Correct Answer: B. Rusting of iron
Explanation:
Rusting forms new iron oxide substances.
Chemical changes involve rearrangement of atoms and new products.
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Correct Answer: B. Mass of component divided by total mass times 100%
Explanation:
Mass percent expresses composition on a mass basis.
All component mass percentages sum to 100%.