1. 1
   A data table in a textbook lists the relative atomic mass ($A_r$) of copper as 63.5 and of bromine as approximately 80.

   (a)

   A data table states that copper has a relative atomic mass ($A_r$) of 63.5. Which statement correctly defines relative atomic mass?

   [1 mark]

   • AAn average value for the isotopes of an element, compared with carbon-12
   • BThe mass, in grams, of one mole of the element
   • CThe mass number of the single most common isotope
   • DThe total number of protons and neutrons in every isotope added together

   (b)

   Relative atomic mass values are calculated by comparing the mass of atoms of an element with the mass of atoms of which reference isotope?

   [1 mark]

   • AHydrogen-1
   • BOxygen-16
   • CCarbon-12
   • DCopper-63

   (c)

   Explain why the relative atomic mass of copper, 63.5, is not a whole number.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A table lists boron with a relative atomic mass of 10.8 and magnesium with a relative atomic mass of 24.3, alongside data showing the different isotopes present in each element and how abundant each isotope is.

   (a)

   What are students expected to be able to do with such isotope abundance data at this level?

   [1 mark]

   • AStudents must always calculate relative atomic mass from the given isotope percentages
   • BStudents are not expected to calculate relative atomic mass from isotopic abundance data
   • CStudents must convert isotope abundance data into mass numbers only
   • DStudents must use isotope abundance data to identify the atomic number of the element

   (b)

   Which of the following best describes how the relative atomic mass values in the table, such as boron's 10.8, are obtained?

   [1 mark]

   • AThey are found by counting the total number of isotopes an element has
   • BThey are measured directly using a simple laboratory balance
   • CThey are equal to the atomic number of the element
   • DThey are given as a known average value for the naturally occurring isotopes of the element

   (c)

   State why, at this level, a student is expected to use a given relative atomic mass value directly rather than working it out from isotopic abundance data.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student sees that one isotope of lithium has a mass number of 7, but the relative atomic mass of lithium given in a data table is 6.9.

   (a)

   Explain the difference between 'mass number' and 'relative atomic mass'.

   [3 marks]

   (b)

   Explain why the relative atomic mass of lithium, 6.9, is close to 7 but slightly lower, without carrying out any calculation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A student compares two elements: chlorine, whose relative atomic mass is 35.5, and a hypothetical element that exists almost entirely as one isotope, giving it a relative atomic mass very close to a whole number.

   (a)

   Explain what relative atomic mass represents, and explain why some elements have a relative atomic mass that is very close to a whole number while others, such as chlorine with a relative atomic mass of 35.5, are clearly not whole numbers.

   [6 marks]

   (b)

   Explain why chemists use relative atomic mass, rather than the mass of just one isotope, when carrying out calculations involving the masses of elements and compounds.

   [6 marks]

   Total for question 4: 12 marks

End of questions