MCQ Collection
ECAT MCQs
Practice ECAT questions with answers and explanations.
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A.
Carry electrons between electrodes
B.
Increase electrode mass only
C.
Maintain electrical neutrality by ion migration
D.
Stop all ion movement
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Correct Answer: C. Maintain electrical neutrality by ion migration
Explanation:
The salt bridge completes the internal ionic circuit.
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A.
Stoichiometric coefficients only
B.
Equilibrium composition only
C.
Heat released by reaction
D.
Dependence of reaction rate on reactant concentrations
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Correct Answer: D. Dependence of reaction rate on reactant concentrations
Explanation:
A rate law is determined experimentally.
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A.
A nonspontaneous reaction under all conditions
B.
No electron transfer
C.
Zero equilibrium constant
D.
A spontaneous cell reaction under standard conditions
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Correct Answer: D. A spontaneous cell reaction under standard conditions
Explanation:
Positive E° corresponds to negative standard Gibbs energy.
Choose an option to check your answer.
A.
Exponent of a concentration term in a rate law
B.
Stoichiometric coefficient in every case
C.
Number of products
D.
Activation energy
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Correct Answer: A. Exponent of a concentration term in a rate law
Explanation:
Reaction order may be zero, fractional, or integer.
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A.
Use of electrical current to cause chemical change
B.
Spontaneous production of current only
C.
Neutralization of acid and base
D.
Heating without reaction
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Correct Answer: A. Use of electrical current to cause chemical change
Explanation:
Electrolysis drives oxidation and reduction at electrodes.
Choose an option to check your answer.
A.
Total enthalpy of products
B.
Minimum energy barrier for a reaction pathway
C.
Energy released by a catalyst
D.
Bond energy of every reactant
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Correct Answer: B. Minimum energy barrier for a reaction pathway
Explanation:
Reacting particles need sufficient energy and orientation to form an activated complex.
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A.
By increasing equilibrium constant
B.
By increasing product enthalpy
C.
By providing a pathway with lower activation energy
D.
By being permanently consumed
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Correct Answer: C. By providing a pathway with lower activation energy
Explanation:
A catalyst speeds both forward and reverse reactions.
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A.
It favors the side with more gas moles
B.
It never affects equilibrium
C.
It favors the product side
D.
It changes the equilibrium constant at fixed temperature
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Correct Answer: C. It favors the product side
Explanation:
Higher pressure favors the side occupying less gas volume.
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A.
An electron-pair acceptor
B.
A proton donor only
C.
An electron-pair donor
D.
A species with no lone pairs
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Correct Answer: C. An electron-pair donor
Explanation:
Lewis bases donate a lone pair to form a coordinate bond.
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A.
Yes, it always increases K
B.
Yes, it always decreases K
C.
Only for exothermic reactions
D.
No
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Correct Answer: D. No
Explanation:
A catalyst lowers activation energies for both directions.
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A.
Two species differing by one electron
B.
Two isomers
C.
An oxidant and reductant only
D.
Two species differing by one proton
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Correct Answer: D. Two species differing by one proton
Explanation:
An acid forms its conjugate base after donating H+.
Choose an option to check your answer.
A.
It can change K
B.
It never changes K
C.
It changes K only for gases
D.
It changes K only when a catalyst is present
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Correct Answer: A. It can change K
Explanation:
Temperature alters the balance between forward and reverse energetics.
