MCQ Collection
MDCAT Chemistry MCQs
Practice MDCAT Chemistry questions with answers and explanations.
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.
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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.
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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.
Choose an option to check your answer.
A.
It always decreases rate
B.
It increases collision frequency and usually increases rate
C.
It changes only molar mass
D.
It eliminates activation energy
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Correct Answer: B. It increases collision frequency and usually increases rate
Explanation:
More particles per volume collide more often.
Choose an option to check your answer.
A.
It decreases rate
B.
It has no effect
C.
It usually increases rate
D.
It changes equilibrium constant only
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Correct Answer: C. It usually increases rate
Explanation:
More exposed particles are available for collision.
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A.
An acid with low concentration only
B.
An acid with no hydrogen atoms
C.
An acid that ionizes only partially in water
D.
An acid that cannot donate protons
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Correct Answer: C. An acid that ionizes only partially in water
Explanation:
Weak-acid solutions contain both ionized and unionized forms.
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A.
Positive logarithm of hydroxide concentration
B.
Hydrogen concentration multiplied by ten
C.
A direct measure of reaction rate
D.
Negative logarithm of hydrogen-ion activity or approximate concentration
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Correct Answer: D. Negative logarithm of hydrogen-ion activity or approximate concentration
Explanation:
For dilute solutions, pH≈-log[H+].
Choose an option to check your answer.
A.
Negative logarithm of hydroxide-ion concentration
B.
Negative logarithm of hydrogen-ion concentration
C.
Hydroxide concentration itself
D.
Pressure of water vapor
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Correct Answer: A. Negative logarithm of hydroxide-ion concentration
Explanation:
For dilute aqueous solutions, pOH=-log[OH-].
Choose an option to check your answer.
A.
-160 kJ
B.
-40 kJ
C.
+40 kJ
D.
+160 kJ
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Correct Answer: B. -40 kJ
Explanation:
Use ΔG=ΔH-TΔS.
Choose an option to check your answer.
A.
A solution with pH exactly 7
B.
A strong acid only
C.
A solution that resists large pH changes
D.
A saturated salt solution only
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Correct Answer: C. A solution that resists large pH changes
Explanation:
Buffers contain a weak acid-base pair.
Choose an option to check your answer.
A.
+30 kJ
B.
+130 kJ
C.
-30 kJ
D.
-130 kJ
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Correct Answer: C. -30 kJ
Explanation:
Use ΔG=50-400(0.20).
