MCQ Collection
Pakistan MCQs
Practice Pakistan questions with answers and explanations.
Choose an option to check your answer.
A.
A species that accepts electrons and is reduced
B.
A neutral salt only
C.
A species that causes reduction and is itself oxidized
D.
An electrode that never reacts
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Correct Answer: C. A species that causes reduction and is itself oxidized
Explanation:
The reducing agent donates electrons.
Choose an option to check your answer.
A.
A cell requiring external electrical energy
B.
A nonredox reaction vessel
C.
A calorimeter
D.
An electrochemical cell producing electrical energy from a spontaneous reaction
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Correct Answer: D. An electrochemical cell producing electrical energy from a spontaneous reaction
Explanation:
A galvanic or voltaic cell converts chemical energy into electrical energy.
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A.
A cell using electrical energy to drive a nonspontaneous reaction
B.
A spontaneous battery only
C.
A gas-law apparatus
D.
A buffer system
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Correct Answer: A. A cell using electrical energy to drive a nonspontaneous reaction
Explanation:
Electrolysis requires an external power source.
Choose an option to check your answer.
A.
At the cathode
B.
At the anode
C.
In the salt bridge only
D.
At both electrodes equally
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Correct Answer: B. At the anode
Explanation:
The mnemonic 'An Ox' identifies oxidation at the anode.
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A.
At the anode
B.
In the wire only
C.
At the cathode
D.
In the solvent only
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Correct Answer: C. At the cathode
Explanation:
The mnemonic 'Red Cat' identifies reduction at the cathode.
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A.
Total mass of products
B.
Equilibrium constant
C.
Heat capacity
D.
Change in concentration of reactant or product per unit time
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Correct Answer: D. Change in concentration of reactant or product per unit time
Explanation:
Reaction rate measures how fast composition changes.
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A.
Carry electrons between electrodes
B.
Increase electrode mass only
C.
Stop all ion movement
D.
Maintain electrical neutrality by ion migration
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Correct Answer: D. Maintain electrical neutrality by ion migration
Explanation:
The salt bridge completes the internal ionic circuit.
Choose an option to check your answer.
A.
Dependence of reaction rate on reactant concentrations
B.
Stoichiometric coefficients only
C.
Equilibrium composition only
D.
Heat released by reaction
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Correct Answer: A. Dependence of reaction rate on reactant concentrations
Explanation:
A rate law is determined experimentally.
Choose an option to check your answer.
A.
Stoichiometric coefficient in every case
B.
Exponent of a concentration term in a rate law
C.
Number of products
D.
Activation energy
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Correct Answer: B. Exponent of a concentration term in a rate law
Explanation:
Reaction order may be zero, fractional, or integer.
Choose an option to check your answer.
A.
Total enthalpy of products
B.
Energy released by a catalyst
C.
Minimum energy barrier for a reaction pathway
D.
Bond energy of every reactant
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Correct Answer: C. Minimum energy barrier for a reaction pathway
Explanation:
Reacting particles need sufficient energy and orientation to form an activated complex.
Choose an option to check your answer.
A.
By increasing equilibrium constant
B.
By increasing product enthalpy
C.
By being permanently consumed
D.
By providing a pathway with lower activation energy
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Correct Answer: D. By providing a pathway with lower activation energy
Explanation:
A catalyst speeds both forward and reverse reactions.
Choose an option to check your answer.
A.
Higher temperature increases rate
B.
Higher temperature always decreases rate
C.
Temperature has no effect
D.
Only equilibrium changes, never rate
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Correct Answer: A. Higher temperature increases rate
Explanation:
Higher temperature increases collision frequency and energetic collisions.
