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CAIE A-Level Chemistry 22.2.2 Relative Atomic Mass from Isotopes

Practise calculating relative atomic mass as the abundance-weighted mean of isotopic masses from data or spectra.

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

22.2.2—The atomic mass of an element question 1

[Maximum number: 1]

Copper is used in electrical equipment. It has a melting point of 1085∘C1085^{\circ} \mathrm{C}.

The relative isotopic masses and natural abundances of the two isotopes in a sample of copper are shown in Table 1.1.

Table 1.1

Table 1.1

Calculate the relative atomic mass, ArA_{\mathrm{r}}, of copper in this sample using the data in Table 1.1.

Show your working.

Ar=A_{r}=
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