Set 5 Chemistry [Paper] 2

1 SECTION A (60 Marks) Answer only three questions from this section . 1.(a) Describe, using equations where applicable, the reactions of chromium with: (i) Air. (ii) Sodium hydroxide solution. (iii)Sulphuric acid. (08 marks) b) (i).Explain why chromium is considered a typical transition metal element. (02 marks) (ii) State five ways in which the chemistry of chromium is s imilar to that of aluminium . (05 marks) c) (i) State what is observed when a small piece of magnesium ribbon is dropped in to a solution of chromium (III) sulphate. (02 marks) (ii) Explain the observation in c ( i) above . (03 marks) 2. The mass spectrometer can be used to determine the relative atomic mass of elements consisting of various isotopes. a) What is meant by the following terms: (@01 mark) (i) Relative intensities. (ii) Relative abundance. (iii) Relative atomic mass. b) Briefly describe how the relative atomic mass of mass metal which consists of three isotopes can be determined using a mass spectrometer .[Diagram not required] (06 marks) c) The relative atomic mass of magnesiu m with isotopes 𝑀𝑔1224, 𝑀𝑔1225 & 𝑀𝑔1226 is 24.3.If the percentage abundance of 𝑀𝑔1225 & 𝑀𝑔1226 are equal. (i) Calculate the percentage abundance of each isotope of magnesium . (01½ marks) (ii) Sket ch the mass spectrum of magnesium . (02 marks) d) The table below shows the results of radioactive decay of a radioactive isotope of magnesium 𝑀𝑔1226.Use the data to plot a graph of log(mass) against time. (04 marks) 2 Mass of 𝑀𝑔1226(g) 18.7 14.6 11.3 8.8 6.9 5.4 Time (s) 300 600 900 1,200 1,500 1,800 e) Using the graph plotted in (d) above determine the: (i) Order of radioactive decay of𝑀𝑔1226. (01 mark) (ii) Rate constant and h ence half -life of𝑀𝑔1226. (01½ marks) (iii) Original mass of𝑀𝑔1226. …