Set 3 Chemistry [Paper] 2

Page 1 of 5 SECTION A Attempt only three questions in this section. 1.a) Define the term relative atomic mass . (02 marks) 1.b) Explain how relative atomic mass can be determined by the mass spectrometer . (09 marks) 1.c) The mass spectrum of an element Q contained four lines at mass/charge of 54, 56, 57 & 58 with relative intensities of 5.84 , 91.68 , 2.17 & 0.31 respectively. i. Explain what the term relative intensities mean and why the mass spectrum of element Q contains 4 lines . (03 marks) ii. Calculate the relative atomic mass of element Q. (02 marks) 1.d) Explain why the values of relative atomic mass have no units. (01 mark) 1.e) Thorium decays according to the equation below. 𝑇ℎ90232 + α X +β Y + β Z Determine the mass numbers and atomic numbers of X, Y & Z. (03 marks) 2.a) Explain the term melting point . (01 mark) 2.b) State the factors which affect the melting point : (@01 mark) i. Metals. ii. Molecular substances . 2.c) Explain the trend in melting points of the elements in group (II) and group (VII) of the periodic table. (05 marks) 2.d) Explain why transition metals of period 4 tend to have higher melting points than non -transition metals of the same period. (02 marks) 2.e) The table below shows melting points of some compounds . Compounds Melting point/K Aluminium oxide 2290 Aluminium chloride 451 Calcium oxide 2850 Calcium chloride 1051 Explain why: i. The melting point of aluminium chloride is abnormally low compared to that of aluminium oxide. (02 marks) ii. The melting point of calcium oxide is much higher than that of calcium chloride. (02 marks) Page 2 of 5 2.f) Determine the freezing point depression for a solution containing 0.025g of …