14 (B410U10-1) Examiner only 13. Compound X contains only carbon, hydrogen and oxygen. 6.57 g of X was burned in excess oxygen to form carbon dioxide and water. 12.57 g of carbon dioxide and 7.74 g of water were collected. (a) Suggest how the mass of carbon dioxide and the mass of water could be measured in this experiment. [2] (b) Find the percentage by mass of each element in X. [3] Percentage carbon = ..................................... % Percentage hydrogen = ..................................... % Percentage oxygen = ..................................... % (c) Calculate the empirical formula of X. [2] Empirical formula .......................................................... © WJEC CBAC Ltd. (B410U10-1) Turn over. 15 Examiner only (d) 9.20 g of X, measured at a pressure of 103 kPa and a temperature of 100 °C, had a volume of 6.02 × 103 cm3. Calculate the relative molecular mass, Mr , of X. [4] Relative molecular mass = ....................................................... (e) Use your answers to parts (c) and (d) to deduce the molecular formula of X. [1] Molecular formula .................................................................. END OF PAPER © WJEC CBAC Ltd. 12 Examiner only (B410U10-1) 16 © WJEC CBAC Ltd. For continuation only.