8 4 This question is about isotopes. (a) The table shows data for some isotopes of potassium. Isotope Relative isotopic mass Abundance % 39K 38.9637 93.218 40K 39.9340 0.012 41K 40.9618 6.770 (i) State what is meant by the terms ‘relative isotopic mass’ and ‘relative atomic mass’. 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(ii) State what is meant by the term ‘isotopes’. Illustrate your answer by referring to the isotopes of potassium. 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(iii) Use the data in the table to calculate the relative atomic mass of potassium. Give your answer to 4 significant figures. (2) 9 Turn over (b) The relative isotopic abundances of an element can be measured using a mass spectrometer. A simplified and incompletely labelled diagram of a mass spectrometer is shown. X + vaporised sample to vacuum pump detector A B C (i) Name the feature of the mass spectrometer responsible for the behaviour of the ions in the region indicated by the arrow X. (1) .................................................................................................................................................................................................................................................................................... (ii) Explain the three ion pathways, A, B and C, shown in the region indicated by the arrow X. 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(iii) Give a reason why the mass spectrometer must be operated under vacuum. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 4 = 12 marks)