MCQ Collection
Pakistan MCQs
Practice Pakistan questions with answers and explanations.
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Correct Answer: C. Dynamic state where forward and reverse reaction rates are equal
Explanation:
At equilibrium, concentrations remain constant over time.
Molecules continue reacting in both directions.
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Correct Answer: D. A ratio of product and reactant activities at equilibrium
Explanation:
The equilibrium expression follows stoichiometric powers.
Its value depends on temperature.
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Correct Answer: A. Products are strongly favored at equilibrium
Explanation:
A large K means the equilibrium mixture contains mostly products.
It does not directly indicate reaction speed.
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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.
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Correct Answer: C. A process releasing heat to the surroundings
Explanation:
Exothermic processes have negative enthalpy change under the usual convention.
The surroundings gain heat.
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Correct Answer: D. A process absorbing heat from the surroundings
Explanation:
Endothermic processes have positive enthalpy change.
The system gains heat.
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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.
