6   3 This question is about the molar masses of three organic compounds, X, Y and Z. (a) The accurate relative atomic masses, Ar , of four of the elements that could be present in an organic compound are shown. Element Ar hydrogen, H 1.0078 carbon, C 12.0000 nitrogen, N 14.0031 oxygen, O 15.9949 The mass spectrum of organic compound X gives a molecular ion peak at m/z = 60.0323 What is compound X? (1) A ethanamide, CH3CONH2 B ethanoic acid, CH3COOH C trimethylamine, (CH3)3N D urea, CO(NH2)2 (b) 9.90 g of a gaseous organic compound, Y, occupies a volume of 5.40 dm3 at room temperature and pressure (r.t.p.). Calculate the molar mass of the compound Y. [molar gas volume at r.t.p. = 24.0 dm3 mol–1] (2) Turn over 7   (c) A quantity of a volatile organic liquid, Z, is placed in a 60.0 cm3 flask and heated to 95.0°C. When all the liquid has vaporised, the flask is sealed. Mass of vapour = 0.170 g Pressure = 100.6 kPa Gas constant (R) = 8.31 J mol–1 K–1 Calculate the molar mass of compound Z, giving your answer to an appropriate number of significant figures. Assume there was no air left in the flask once the liquid Z had vaporised. (4) (Total for Question 3 = 7 marks)