MCQ Collection
ECAT Chemistry MCQs
Practice ECAT Chemistry questions with answers and explanations.
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Correct Answer: D. Melting of ice
Explanation:
A physical change alters form or state without changing chemical identity.
Ice and liquid water are both H2O.
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Correct Answer: A. Rusting of iron
Explanation:
Rusting forms new iron oxide substances.
Chemical changes involve rearrangement of atoms and new products.
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Correct Answer: B. Mass per unit volume
Explanation:
Density describes how much mass is packed into a volume.
It is commonly expressed in g/cm³ or kg/m³.
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Correct Answer: C. mole
Explanation:
The mole is the SI base unit for amount of substance.
One mole contains Avogadro's number of specified entities.
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Correct Answer: D. 6.022 × 10^23
Explanation:
Avogadro's constant gives the number of entities in one mole.
The entities may be atoms, molecules, ions, or formula units.
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Correct Answer: A. Mass of one mole of a substance
Explanation:
Molar mass is numerically related to relative atomic or molecular mass.
Its common unit is g/mol.
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Correct Answer: B. The simplest whole-number ratio of atoms in a compound
Explanation:
An empirical formula shows the lowest integer ratio of elements.
It may differ from the molecular formula.
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Correct Answer: C. The actual number of each type of atom in one molecule
Explanation:
A molecular formula is a whole-number multiple of the empirical formula.
It applies to substances composed of discrete molecules.
