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Class 9 Chemistry · Chapter 2 · Test 5

Relative Atomic Mass

20 MCQs • Practice relative atomic mass, isotopic abundance, weighted averages, atomic mass units, and numerical calculations.

MCQs

20 questions · 20 min · 20 marks

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Sample questions

The first 5 of 20. Try each one, then tap to see the answer.

  1. Question 1

    What is relative atomic mass?

    • AThe mass of one proton
    • BThe weighted average mass of an element's atoms compared with one twelfth of carbon-12
    • CThe total number of neutrons in an atom
    • DThe mass number of the most common isotope
    Show answer

    Answer: B

    Relative atomic mass is the weighted average of isotope masses compared with one twelfth of the mass of carbon-12.

  2. Question 2

    How is one atomic mass unit defined?

    • AThe mass of one hydrogen atom
    • BThe mass of one proton
    • COne twelfth of the mass of a carbon-12 atom
    • DThe mass of one neutron
    Show answer

    Answer: C

    One atomic mass unit is defined as one twelfth of the mass of a carbon-12 atom.

  3. Question 3

    Why is the relative atomic mass of an element often not a whole number?

    • AIt includes the mass of electrons only
    • BIt is usually a weighted average of naturally occurring isotopes
    • CIt is always equal to the neutron number
    • DIt changes randomly during chemical reactions
    Show answer

    Answer: B

    The relative atomic mass accounts for the masses and natural abundances of an element's isotopes.

  4. Question 4

    What does isotopic abundance describe?

    • AThe number of protons in an isotope
    • BThe percentage of an isotope present in a natural sample
    • CThe number of electron shells
    • DThe rate of chemical reaction
    Show answer

    Answer: B

    Isotopic abundance is the percentage of a particular isotope in a natural sample of an element.

  5. Question 5

    An element has two isotopes with abundances of 60% and 40%. What is the total abundance?

    • A80%
    • B90%
    • C100%
    • D120%
    Show answer

    Answer: C

    The total abundance of all isotopes in a sample is 100%.

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