Science: Double Award

Transcription

1 Centre Number Candidate Number For Examiner s Use Surname Other Names Candidate Signature Examiner s Initials AQA Level 1/2 Certificate Higher Tier June 2015 Science: Double Award Chemistry Paper 2H Tuesday 9 June pm to 2.30 pm 8404/C/2H H Question TOTAL Mark For this paper you must have: a ruler a calculator the periodic table (enclosed). Time allowed 1 hour Instructions Use black ink or black ball-point pen. Fill in the es at the top of this page. Answer all questions. You must answer the questions in the spaces provided. around each page or on blank pages. Do all rough work in this book. Cross through any work you do not want to be marked. Information The marks for questions are shown in brackets. The maximum mark for this paper is 60. You are expected to use a calculator where appropriate. You are reminded of the need for good English and clear presentation in your answers. Question 1(c) should be answered in continuous prose. In this question you will be marked on your ability to: use good English organise information clearly use specialist vocabulary where appropriate. Advice In all calculations, show clearly how you work out your answer. (JUN158404C2H01) P82788/Jun15/E5 8404/C/2H

2 2 Answer all questions in the spaces provided. 1 This question is about separating mixtures. 1 (a) Figure 1 shows the apparatus a student used to separate sand and water. Figure 1 Funnel Mixture of sand and water 1 (a) (i) Name the separation process. 1 (a) (ii) There is something wrong with the apparatus in Figure 1. Explain why the apparatus in Figure 1 would not separate the mixture. [2 marks] (02)

3 3 1 (b) Figure 2 shows the apparatus a student used to separate ethanol and water. Figure 2 Water out Condenser Mixture of ethanol and water Water in Heat 1 (b) (i) Name the separation process. 1 (b) (ii) There is something wrong with the apparatus in Figure 2. Explain why the apparatus in Figure 2 would not separate the mixture. [2 marks] Question 1 continues on the next page Turn over s (03)

4 4 1 (c) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Paper chromatography is used to separate mixtures. Figure 3 shows the result of a chromatography experiment to separate the dyes in a sample of black ink. Figure 3 Final water level Yellow dye Red dye Blue dye Start line Describe how the paper chromatography experiment is done. [6 marks] (04)

5 5 Extra space... 1 (d) The R f value of a dye is calculated using the equation: R f ¼ distance moved by dye from the start line distance moved by water from the start line Calculate the R f value of the red dye in Figure 3. Show your working. [3 marks] R f value ¼ Turn over for the next question Turn over s (05)

6 6 2 This question is about rates of reaction. Dilute hydrochloric acid reacts with sodium thiosulfate solution. 2HClðaqÞ + Na 2 S 2 O 3 ðaqþ fi 2NaClðaqÞ + SðsÞ + SO 2 ðgþ + H 2 OðlÞ 2 (a) The reaction produces a precipitate. What is the name of the precipitate? Tick (3) one. Sodium chloride Sulfur Sulfur dioxide Water (06)

7 7 2 (b) A student investigated how the rate of a reaction changes with temperature. The student used the following method: put 50 cm 3 of sodium thiosulfate solution into a conical flask heat the sodium thiosulfate solution to the required reaction temperature put the flask on a cross drawn on a piece of paper add 10 cm 3 of dilute hydrochloric acid and start a stopclock stop the stopclock when the cross can no longer be seen. Figure 4 Add dilute acid and start timing Sodium thiosulfate solution A cross drawn on paper Before After 2 (b) (i) Why can the student no longer see the cross? Question 2 continues on the next page Turn over s (07)

8 8 2 (b) (ii) The student s results are shown in Table 1. Table 1 Temperature in o C Time in seconds (08)

9 9 Plot the results on the grid in Figure 5, choosing appropriate scales. Draw a best-fit smooth curve. [4 marks] Figure 5 Time in seconds Temperature in C 2 (b) (iii) Draw a ring around the anomalous point on the graph. Turn over s (09)

10 10 2 (b) (iv) There was a systematic error in the student s method on page 7. Explain why the error in the method made the temperatures recorded in Table 1 inaccurate. Suggest an improvement to the method that would make the recorded temperatures more accurate. [3 marks] 2 (c) The student calculated the rate of each reaction by calculating 1/time. She plotted a graph showing the rate of the reaction and the temperature. Figure 6 shows the best-fit graph she drew Figure 6 Rate in s Temperature in C (10)

11 11 2 (c) (i) How does the graph in Figure 6 show that the reaction is faster at higher temperatures? 2 (c) (ii) Explain, in terms of particles, why the reaction is faster at higher temperatures. [3 marks] 2 (c) (iii) The student said that the graph in Figure 6 shows that rate is directly proportional to temperature. Give a reason why the student was not correct. 15 Turn over for the next question Turn over s (11)

12 12 3 A student investigated displacement reactions of metals. 3 (a) The student measured the temperature change when different metals react with copper sulfate solution. He used the following method: put 50 cm 3 of copper sulfate solution into a polystyrene cup measure the temperature of the solution calculate the mass of mol of the metal add this mass of metal to the solution and stir the mixture measure the temperature of the mixture after one minute. 3 (a) (i) Name a suitable piece of apparatus the student could use to measure 50 cm 3 of copper sulfate solution. 3 (a) (ii) Calculate the mass of mol of zinc. Relative atomic mass (A r ): Zn ¼ 65 [2 marks] Mass ¼... g 3 (a) (iii) Give a reason why the student used a polystyrene cup instead of a glass beaker. (12)

13 13 3 (a) (iv) Figure 7 shows the readings on the thermometer in one of the experiments. Figure 7 Temperature at start Temperature after one minute C 50 C Write down the temperature at the start and after one minute. [2 marks] Temperature at the start ¼... C Temperature after one minute ¼... C 3 (a) (v) Use your answers from part (a)(iv) to calculate the temperature increase. Temperature increase ¼... C Question 3 continues on the next page Turn over s (13)

14 14 3 (b) The student did the experiment three times for each metal. Table 2 shows the student s results. Table 2 Metal Temperature increase in o C Experiment 1 Experiment 2 Experiment 3 Mean Zinc Iron Magnesium (b) (i) Calculate the mean temperature increase for zinc and for magnesium. You should take account of any anomalous results. [2 marks] Zinc... Mean temperature increase ¼... C Magnesium... Mean temperature increase ¼... C 3 (b) (ii) Which metal has the most precise results? Give a reason for your answer. [2 marks] Metal... Reason... (14)

15 15 3 (b) (iii) Use the results in Table 2 to put the metals copper, iron, magnesium and zinc in order of their reactivity. Explain how you worked out the order of reactivity. [4 marks] Most reactive Least reactive... Explanation... 3 (c) The student wanted to make sure his results were valid. The variables he controlled were the volume of copper sulfate solution, the number of moles of metal and the time when the temperature was measured. The metal was in excess. Suggest one other control variable. Explain how the temperature change would be affected if this variable was not controlled. [3 marks] Control variable... Explanation Turn over for the next question Turn over s (15)

16 16 4 This question is about the extraction of aluminium. 4 (a) Aluminium is produced by electrolysing a molten mixture of aluminium oxide and cryolite. Aluminium oxide is ionic. 4 (a) (i) Explain why the aluminium oxide must be molten for electrolysis. [2 marks] 4 (a) (ii) Explain how adding cryolite reduces the cost of the process. [2 marks] 4 (a) (iii) Complete and balance the half equation for the reaction at the negative electrode (cathode). Al 3þ fi Al 4 (b) Aluminium oxide is obtained by purifying aluminium ore. The purification process produces a lot of waste called red mud. A scientist analysed the red mud. The scientist added sulfuric acid to the red mud and filtered the mixture. The scientist then added sodium hydroxide solution, drop by drop until in excess, to the filtrate. A brown precipitate formed. 4 (b) (i) State the ion that the red mud must contain to produce the brown precipitate. (16)

17 17 4 (b) (ii) No precipitate formed until several drops of sodium hydroxide solution had been added. Suggest why. 4 (b) (iii) Describe what you would see if sodium hydroxide solution is added, drop by drop until in excess, to a solution of aluminium sulfate. [2 marks] 4 (c) The equation for the production of aluminium from aluminium oxide is: 2Al 2 O 3 fi 4Al + 3O 2 Calculate the mass of aluminium produced from 408 tonnes of aluminium oxide. Relative atomic masses (A r ): O ¼ 16; Al ¼ 27 [3 marks] Mass ¼... tonnes 12 END OF QUESTIONS (17)

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20 20 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Acknowledgement of copyright-holders and publishers Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright-holders have been unsuccessful and AQA will be happy to rectify any omissions of acknowledgements in future papers if notified. Copyright ª 2015 AQA and its licensors. All rights reserved. (20)