MCQ Collection
ECAT MCQs
Practice ECAT questions with answers and explanations.
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Correct Answer: D. Electronic transitions within split d orbitals absorb visible light
Explanation:
Ligands split d-orbital energies.
Absorption of selected visible wavelengths gives the observed complementary color.
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Correct Answer: A. Their ns and (n-1)d electrons have similar energies
Explanation:
Both s and d electrons may participate in bonding or ion formation.
This permits several stable oxidation states.
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Correct Answer: B. An ion or molecule donating an electron pair to a metal center
Explanation:
Ligands act as Lewis bases.
They form coordinate covalent bonds with metal ions.
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Correct Answer: D. 9
Explanation:
At 25°C, pH+pOH=14.
POH=14-5 = 9.
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Correct Answer: D. An oxide that reacts with both acids and bases
Explanation:
Amphoteric oxides can behave as acidic or basic substances.
Aluminum oxide and zinc oxide are examples.
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Correct Answer: A. 0.40 M
Explanation:
Moles NaOH=0.0200×0.50=0.0100 mol.
The HCl concentration is 0.0100/0.0250=0.40 M.
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Correct Answer: B. 0.10 M/s
Explanation:
For first order, rate=k[A].
Rate=0.20×0.50=0.10 M/s.
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Correct Answer: C. 4
Explanation:
The rate depends on the square of concentration.
Doubling gives 2²=4 times the rate.
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Correct Answer: D. +6
Explanation:
Four oxygens contribute -8 total.
Sulfur must be +6 so the ion total is -2.
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Correct Answer: A. +7
Explanation:
Potassium is +1 and four oxygens total -8.
Manganese must be +7 for a neutral compound.
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Correct Answer: B. 1.20 V
Explanation:
Use E°cell=E°cathode-E°anode.
0.80-(-0.40)=1.20 V.
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Correct Answer: C. Oxygen
Explanation:
Oxygen is the most abundant element in Earth's crust by mass.
It occurs mainly in oxides and silicate minerals.
