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CAIE A-Level Chemistry AS 22.2.2 The Atomic Mass of an Element Questions

Practise CAIE 9701 relative atomic mass calculations by weighting isotope masses with percentage abundance and distinguishing mass number from neutron count.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • multiply each isotopic mass by its percentage or fractional abundance and add the contributions
  • divide by total abundance when percentages do not already sum in a convenient weighted form
  • distinguish mass number and neutron count when deriving an isotope mass before averaging

CAIE A-Level Chemistry AS 22.2.2 The Atomic Mass of an Element Questions question 1

[Maximum number: 1]

The relative atomic mass of antimony is 121.76 .
Antimony has two isotopes. The mass numbers of the two isotopes differ by two. The isotope with the lower mass number is the more abundant.

What is the percentage abundance of the isotope with the higher mass number?

A

12 %

B

38\%

C

62 %

D

88\%

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