1. A sample of element X contains 69 % of 63X and 31 % of 65X. What is the relative atomic mass of X in this sample? A. 63.0 B. 63.6 C. 65.0 D. 69.0 (Total 1 mark) 2. Consider the relative abundance of the isotopes of element X. Isotope Relative abundance (%) 24 80 25 10 26 10 X X X What is the relative atomic mass of X? A. 24 B. 25 C. Between 24 and 25 D. Between 25 and 26 (Total 1 mark) IB Questionbank Chemistry 1 3. A sample of iron has the following isotopic composition by mass. Isotope 54 Relative abundance / % 5.95 Fe 56 Fe 91.88 57 Fe 2.17 Calculate the relative atomic mass of iron based on this data, giving your answer to two decimal places. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ (Total 2 marks) 4. The relative atomic mass of naturally occurring copper is 63.55. Calculate the abundances of 63 Cu and 65Cu in naturally occurring copper. (Total 2 marks) 5. Silicon has three stable isotopes, 28Si, 29Si and 30Si. The heaviest isotope, 30Si, has a percentage abundance of 3.1 %. Calculate the percentage abundance of the lightest isotope to one decimal place. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ (Total 2 marks) IB Questionbank Chemistry 2 6. Rubidium contains two stable isotopes, 85Rb and 87Rb. The relative atomic mass of rubidium is given in Table 5 of the Data Booklet. (a) Calculate the percentage of each isotope in pure rubidium. State your answers to three significant figures. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... (2) (b) The percentage of each isotope can be checked experimentally using a mass spectrometer. A vaporized sample of pure rubidium is ionized and then accelerated in a mass spectrometer. Outline how the use of a magnetic field and a detector in the mass spectrometer enables the percentages of the two isotopes to be determined. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... (3) (c) State the number of electrons and the number of neutrons present in an atom of 87Rb. Number of electrons: ...................................................................................................................................... Number of neutrons: ...................................................................................................................................... (2) (Total 7 marks) IB Questionbank Chemistry 3 7. What is the relative atomic mass of an element with the following mass spectrum? A. 24 B. 25 C. 26 D. 27 (Total 1 mark) IB Questionbank Chemistry 4
