Pearson Edexcel Level 1/Level 2 GCSE (9 - 1)Chemistry Paper 2

Answer ALL questions. Write your answers in the spaces provided. Some questions must be answered with a cross in a box . If you change your mind about an answer, put a line through the box and then mark your new answer ...

Answer ALL questions. Write your answers in the spaces provided. Some questions must be answered with a cross in a box . If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . 1 The Earth’s atmosphere contains several gases. (a) Figure 1 shows the relative amounts of gases thought to be in the Earth’s early atmosphere. gas relative amount in Earth’s early atmosphere oxygen small carbon dioxide large nitrogen small water vapour large Figure 1 The amount of water vapour in today’s atmosphere is much less than the amount in the Earth’s early atmosphere. Explain why the amount of water vapour in the atmosphere has decreased. (2) ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... .....................................................................................................................................................................................................................................................................................3 Turn over DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA *P52471A0332* (b) The apparatus shown in Figure 2 is used to find the percentage of oxygen in dry air. dry air glass tube copper heat syringe A syringe B Figure 2 Syringe A contains 50 cm3 of dry air and syringe B contains no air. The copper in the glass tube is heated strongly. The air in the apparatus is passed backwards and forwards over the copper until all the oxygen has been removed. (i) The following results were obtained initial volume of air in apparatus = 50 cm3 final volume of gas in apparatus = 40 cm3 Calculate the percentage of oxygen in this sample of dry air. (2) ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... percentage oxygen in the air = .............................................................. (ii) At the end of the experiment, the apparatus and its contents are allowed to cool before the final volume of gas is measured. (1) The apparatus and its contents must be allowed to cool because A reading the volume while the apparatus is hot is dangerous B the glass tube may crack when it is hot and allow air into the apparatus C the gas has expanded when it is hot D the copper reacts with other gases in the air when it is hot4 *P52471A0432* DO NOT