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Chemistry Chapter 6 : Topic 7
Mole Concept
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A chemistry student is given several samples: 12 g of carbon, 32 g of oxygen, and 2 g of hydrogen. Each sample contains a very large number of particles. In chemistry, the term used to express a fixed amount of any substance containing a specific number of particles is called:
Reasoning: A mole is defined as the amount of substance that contains Avogadro’s number (6.02×10²³) of particles, regardless of mass or type of substance.
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A container holds 1 mole of helium gas and another container holds 1 mole of carbon dioxide gas. Although their masses are different, both containers have the same number of particles. This is because:
Reasoning: One mole of any substance contains Avogadro’s number of particles, regardless of its mass or physical nature.
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Which statement correctly explains the significance of Avogadro’s number (6.02×10²³) in chemistry?
Reasoning: Avogadro’s number defines the number of fundamental particles (atoms, molecules, ions) present in one mole of any substance.
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A chemist prepares 1 mole of sodium chloride (NaCl). He states that this sample contains 6.02×10²³ formula units of NaCl. This statement is correct because:
Reasoning: A mole always contains Avogadro’s number of representative particles, whether atoms, molecules, or formula units.
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Which of the following best describes the concept of mole in terms of particle counting?
Reasoning: The mole is a counting unit representing a fixed number 6.02×10²³ of particles.
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If 1 mole of a substance contains 6.02×10²³ particles, then 2 moles of the same substance will contain:
Reasoning: Number of particles = moles × Avogadro’s number=2×6.02×10²³=1.204×10²⁴ particles
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A sample of oxygen gas contains 6.02×10²³ molecules. A student concludes that the sample represents 1 mole of oxygen. This conclusion is correct because:
Reasoning: One mole of any substance contains exactly 6.02×10²³ particles, so the sample equals 1 mole.
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Which of the following best distinguishes mole from mass?
Reasoning: Mole is a counting unit for particles, while mass measures quantity of matter in grams or kilograms.
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A student incorrectly says: “One mole of different substances has the same mass.” This statement is wrong because:
Reasoning: One mole always has the same number of particles, but its mass varies depending on molar mass of the substance.
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Which of the following situations correctly represents the concept of one mole?
Reasoning: One mole is defined as Avogadro’s number of particles;6.02×10²³ atoms of carbon represent 1 mole.
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In a classroom discussion, a teacher says that “mole is similar to a dozen but on a much larger scale.” This analogy is correct because:
Reasoning: Like a dozen (12 items), a mole is also a counting unit but represents a much larger fixed number (6.02×10²³).
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A chemist measures 3 moles of a gas. Without knowing the gas type, he can still determine:
Reasoning: Number of particles can always be determined using:Moles × Avogadro’s number, regardless of substance type.
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Which statement best explains why mole is considered a bridge between microscopic and macroscopic worlds?
Reasoning: Mole relates microscopic particles (atoms/molecules) to measurable laboratory quantities like mass.
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If a sample contains 1.204×10²⁴ particles, how many moles does it represent?
Reasoning: Moles = particles ÷ Avogadro’s number=(1.204×10²⁴)÷(6.02×10²³)=2 moles
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Which of the following is NOT a correct interpretation of mole?
Reasoning: Mole is a counting unit, not a fixed mass; mass depends on the substance’s molar mass.
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