MCQ Collection
ECAT MCQs
Practice ECAT questions with answers and explanations.
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Correct Answer: D. A substance changing color over a characteristic pH range
Explanation:
Acid-base indicators have differently colored protonated and deprotonated forms.
They help identify titration endpoints.
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Correct Answer: D. 1
Explanation:
The equilibrium expression is Kc=[B]/[A]^2.
Kc=0.25/(0.50)^2=1.
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Correct Answer: A. A ratio with the equilibrium-expression form using current concentrations or pressures
Explanation:
Q can be calculated at any stage.
Comparing Q with K predicts the direction of net change.
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Correct Answer: A. Toward products
Explanation:
Because Q<K, more products must form.
The reaction proceeds forward until Q reaches K.
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Correct Answer: B. Toward products
Explanation:
The mixture contains too little product relative to equilibrium.
Net forward reaction increases Q toward K.
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Correct Answer: B. A substance that increases H+ concentration in water
Explanation:
Arrhenius acids produce hydrogen ions in aqueous solution.
The model applies specifically to water.
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Correct Answer: C. Toward reactants
Explanation:
The mixture contains too much product relative to equilibrium.
Net reverse reaction lowers Q toward K.
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Correct Answer: C. A substance that increases OH- concentration in water
Explanation:
Arrhenius bases increase hydroxide-ion concentration in water.
Many metal hydroxides fit this definition.
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Correct Answer: D. How an equilibrium system responds to a disturbance
Explanation:
An equilibrium shifts to oppose an imposed change.
Changes in concentration, pressure, or temperature may shift position.
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Correct Answer: D. A proton donor
Explanation:
Brønsted-Lowry acid-base reactions involve proton transfer.
The acid loses H+ to a base.
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Correct Answer: A. The equilibrium generally shifts toward products
Explanation:
The system consumes some added reactant.
The shift reduces the imposed concentration change.
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Correct Answer: A. A proton acceptor
Explanation:
A Brønsted-Lowry base accepts H+.
It forms its conjugate acid.
