Relative Masses of Atoms and Molecules

Relative Masses of Atoms and Molecules Quiz

Spec 3.2 · Cambridge IGCSE Chemistry: Quiz

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5 questions, one answer each

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  1. 1. What is relative atomic mass (Ar) measured relative to?

    • A. 1/12th of the mass of an atom of carbon-12
    • B. The mass of one hydrogen atom
    • C. The mass of one mole of any element
    • D. 1/6th of the mass of an oxygen atom

  2. 2. What is relative formula mass used for instead of relative molecular mass?

    • A. Elements only
    • B. Ionic compounds, which do not exist as individual molecules
    • C. Isotopes only
    • D. Gases only

  3. 3. What is the relative molecular mass of carbon dioxide, CO2? (Ar: C=12, O=16)

    • A. 28
    • B. 32
    • C. 44
    • D. 16

  4. 4. Why do Ar and Mr have no units?

    • A. Because they are always whole numbers
    • B. Because they are ratios comparing masses, not actual masses
    • C. Because they only apply to gases
    • D. Because they are measured in moles

  5. 5. A sample of magnesium oxide, MgO (Mr = 40), has a mass of 10 g. How many moles does this represent, and what would be the mass of 0.5 mol of MgO?

    • A. 0.25 mol; 20 g
    • B. 0.25 mol; 10 g
    • C. 4 mol; 160 g
    • D. 0.4 mol; 20 g

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