MCQ Collection
ECAT MCQs
Practice ECAT questions with answers and explanations.
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Correct Answer: B. The equilibrium generally shifts toward products
Explanation:
The reaction produces more product to replace what was removed.
This is an application of Le Chatelier's principle.
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Correct Answer: B. An electron-pair acceptor
Explanation:
Lewis theory focuses on electron-pair transfer.
Many metal ions and electron-deficient molecules act as Lewis acids.
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Correct Answer: C. Energy required to break one mole of specified gas-phase bonds
Explanation:
Bond enthalpies are average values for many molecules.
Breaking bonds requires energy, while forming bonds releases energy.
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Correct Answer: D. Energy is conserved
Explanation:
Energy may be transferred as heat or work.
It is not created or destroyed.
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Correct Answer: A. A measure related to energy dispersal and number of accessible microstates
Explanation:
Greater dispersal and more possible arrangements generally mean higher entropy.
Gases usually have higher entropy than liquids or solids.
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Correct Answer: B. A process thermodynamically favored under specified conditions
Explanation:
Spontaneity describes direction, not speed.
A spontaneous reaction may still be very slow.
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Correct Answer: C. A thermodynamic function used to predict spontaneity at constant temperature and pressure
Explanation:
Gibbs energy change is ΔG=ΔH-TΔS.
Negative ΔG indicates a thermodynamically favorable direction.
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Correct Answer: D. ΔG = 0
Explanation:
At equilibrium there is no net driving force for change.
The reaction mixture has minimum Gibbs energy under the conditions.
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Correct Answer: A. 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: A. 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: B. 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: B. A ratio of product and reactant activities at equilibrium
Explanation:
The equilibrium expression follows stoichiometric powers.
Its value depends on temperature.
