MCQ Collection
MDCAT 2026 MCQs
Practice MDCAT 2026 questions with answers and explanations.
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Correct Answer: A. Toward reactants
Explanation:
The mixture contains too much product relative to equilibrium.
Net reverse reaction lowers Q toward K.
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Correct Answer: B. Measurement of heat changes
Explanation:
Calorimeters track temperature changes in known heat capacities.
They help determine reaction or phase-change energy.
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Correct Answer: B. How an equilibrium system responds to a disturbance
Explanation:
An equilibrium shifts to oppose an imposed change.
Changes in concentration, pressure, or temperature may shift position.
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Correct Answer: C. Overall enthalpy change is the sum of enthalpy changes for any reaction pathway
Explanation:
Enthalpy is a state function.
Therefore the path between initial and final states does not affect ΔH.
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Correct Answer: C. The equilibrium generally shifts toward products
Explanation:
The system consumes some added reactant.
The shift reduces the imposed concentration change.
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Correct Answer: D. The part of the universe chosen for study
Explanation:
The system may be a reaction mixture, gas, or other selected matter.
Everything else is called the surroundings.
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Correct Answer: A. Everything outside the thermodynamic system
Explanation:
The surroundings can exchange energy or matter with the system depending on the boundary.
System plus surroundings form the universe.
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Correct Answer: B. A system that exchanges both matter and energy
Explanation:
Open systems allow material flow across their boundaries.
Many industrial reactors are open systems.
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Correct Answer: C. A system that exchanges energy but not matter
Explanation:
A closed system has fixed mass.
Heat or work may still cross its boundary.
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Correct Answer: D. A system that exchanges neither matter nor energy
Explanation:
An ideal isolated system has no interaction with surroundings.
A perfect thermos is an approximate example.
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Correct Answer: A. Total microscopic kinetic and potential energy of a system
Explanation:
Internal energy includes molecular motion, bonding, and interactions.
Only changes in internal energy are directly measured.
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Correct Answer: B. A thermodynamic property equal to internal energy plus pressure-volume term
Explanation:
Enthalpy is H=U+PV.
At constant pressure, enthalpy change equals heat transferred for PV work.
