Q1. A student investigated the rate of reaction between marble and hydrochloric acid. (aq) + H 2

Transcription

1 Q. A student investigated the rate of reaction between marble and hydrochloric acid. The student used an excess of marble. The reaction can be represented by this equation: CaCO 3 (s) + HCl(aq) CaCl (aq) + H O(l) + CO (g) The student used the apparatus shown in the diagram. The student measured the mass of the flask and contents for ten minutes. The results are shown on the graph. Use the graph to answer the questions. (a) (i) Complete the graph by drawing a line of best fit. Use the graph to find the mass of the flask and contents after.8 minutes.... grams Page of 68

2 (iii) The rate of reaction can be measured by the steepness of the graph line. Describe, as fully as you can, how the rate of reaction changes with time in this experiment The mass of the flask and contents decreased during the experiment. Use the equation for this reaction to help you explain why (c) A balance is used to measure the mass of the apparatus. (i) Which balance, A, B, or C, has the highest resolution? Balance A Balance B Balance C The balance with the highest resolution is balance The balance used for this experiment should have a high resolution. Explain why Page of 68

3 (d) The student repeated the experiment using powdered marble instead of marble chips. The rate of reaction between the marble and hydrochloric acid particles was much faster with the powder. Explain why (Total marks) Q. The diagram shows the main parts of an instrumental method called gas chromatography linked to mass spectroscopy (GC-MS). This method separates a mixture of compounds and then helps to identify each of the compounds in the mixture. (a) In which part of the apparatus: (i) is the mixture separated?... is the relative molecular mass of each of the compounds in the mixture measured?... Page 3 of 68

4 (i) Athletes sometimes take drugs because the drugs improve their performance. One of these drugs is ephedrine. Ephedrine has the formula: C 0 H 5 NO What relative molecular mass (M r ) would be recorded by GC-MS if ephedrine was present in a blood sample taken from an athlete? Show clearly how you work out your answer. Relative atomic masses: H = ; C = ; N = 4; O = Relative molecular mass =... Another drug is amphetamine which has the formula: C 9 H 3 N The relative molecular mass (M r ) of amphetamine is 35. Calculate the percentage by mass of nitrogen in amphetamine. Relative atomic mass: N = Percentage of nitrogen =... % (c) Athletes are regularly tested for drugs at international athletics events. An instrumental method such as GC-MS is better than methods such as titration. Suggest two reasons why Page 4 of 68

5 (d) When a blood sample is taken from an athlete the sample is often split into two portions. Each portion is tested at a different laboratory. Suggest why (Total 0 marks) Q3. A student heated some hydrated copper sulfate crystals. The equation for this reaction is shown below. CuSO 4.5H O(s) CuSO 4(s) + 5HO hydrated copper sulfate crystals anhydrous copper sulfate water The diagram shows the apparatus used. (a) Name liquid A... What helped the vapour to condense into liquid A? Page 5 of 68

6 (c) Put a tick ( ) next to the correct meaning of the symbol Meaning ( ) equal amounts of reactants and products exothermic reaction reversible reaction (d) The student weighed the copper sulfate before and after it was heated. The experiment was repeated and the two sets of results are shown in the table. Mass of copper sulfate before heating in grams Mass of copper sulfate after heating in grams Mass lost in grams (i) Draw a ring around the average mass lost for these two sets of results g 0.87 g 0.89 g The student used the same mass of copper sulfate each time but the mass lost was different. Put a tick ( different. ) next to the two reasons which could explain why the mass lost is Reason ( ) The student used different test tubes for the two experiments. The student made errors in weighing during the experiments. The student used more ice in one of the experiments. The student did not heat the copper sulfate for long enough in one of the experiments. Page 6 of 68

7 (e) Anhydrous copper sulfate is used to test for water. Use words from the box to complete the sentence. blue green red white Water changes the colour of anhydrous copper sulfate from... to.... (Total 8 marks) Q4. An indigestion tablet contains sodium hydrogencarbonate and citric acid. When the tablet is added to cold water a chemical reaction takes place and there is a lot of fizzing. (a) The formula of the gas that causes the fizzing is CO Name this gas.... This chemical reaction is endothermic. (i) Tick ( ) the statement which describes what happens to the temperature of the solution. Statement Tick ( ) The temperature of the solution will increase. The temperature of the solution will decrease. The temperature of the solution will stay the same. Page 7 of 68

8 Tick ( ) the statement which describes what happens to the energy during the reaction. Energy is given out to the surroundings. Energy is taken in from the surroundings. No energy is given out to or taken from the surroundings. Statement Tick ( ) (Total 3 marks) Q5. Read the article and then answer the questions that follow. Hydrogen fuel for cars? Hydrogen is an excellent fuel. On combustion it reacts with oxygen from the air to release a large amount of energy. The only product of combustion is water which does not cause pollution. Hydrogen gas can be stored under pressure in a cylinder but a leak of the gas could cause an explosion. It has been found that lithium nitride can absorb and then release large volumes of hydrogen. Hydrogen stored in lithium nitride will not explode. The problem is that the rate at which hydrogen is absorbed and then released from normal sized particles of lithium nitride is slow. Recently scientists have made nanosized particles of lithium nitride. The nanosized particles have the advantage that they absorb and release the hydrogen much faster when needed in the fuel cell. (a) Use information from the article to help you to answer these questions. (i) Give two reasons why hydrogen is an excellent fuel Page 8 of 68

9 Hydrogen stored in lithium nitride is safer in an accident than a cylinder full of hydrogen gas. State why. (iii) What is the advantage of using nanosized particles of lithium nitride instead of normal sized particles for storing hydrogen? Lithium nitride is an ionic compound that contains lithium ions (Li + ) and nitride ions (N 3 ). (i) The periodic table on the Data Sheet may help you to answer this question. Which diagram, A, B or C, represents the electronic structure of a lithium atom? Write your answer in the box. Diagram Tick ( ) the statement which describes how a lithium atom (Li) changes into a lithium ion (Li + ). Statement Tick ( ) A lithium atom loses a neutron. A lithium atom loses an electron. A lithium atom loses a proton. Page 9 of 68

10 (iii) The diagram shows the electronic structure of a nitrogen atom. Which diagram, A, B or C, represents the electronic structure of a nitride ion (N 3 )? Write your answer in the box. Diagram (c) The equation for the reaction of lithium nitride with hydrogen is: Li 3 N + H LiNH + LiH What does the symbol mean? Draw a ring around your answer. reversible reaction endothermic reaction neutralisation (d) Draw a ring around the correct answer in each box to complete the sentences. (i) Nanosized particles of lithium nitride will be much larger a little larger much smaller than normal sized particles of lithium nitride. One of the reasons why nanosized particles have different properties from normal sized particles is that they have a greater density mass surface area than normal sized particles of lithium nitride. (Total 0 marks) Page 0 of 68

11 Q6. A student investigated the rate of reaction between marble and hydrochloric acid. The student used an excess of marble. The reaction can be represented by this equation. CaCO 3 (s) + HC (aq) CaC (aq) + H O (l) + CO (g) The student used the apparatus shown in the diagram. The student measured the mass of the flask and contents every half minute for ten minutes. The results are shown on the graph. Use the graph to answer the questions. (a) Complete the graph opposite by drawing a line of best fit. Why did the mass of the flask and contents decrease with time? Page of 68

12 (c) After how many minutes had all the acid been used up?... minutes (d) The student repeated the experiment at a higher temperature. All other variables were kept the same as in the first experiment. The rate of reaction was much faster. (i) Draw a line on the graph to show what the results for this second experiment might look like. Why does an increase in temperature increase the rate of reaction? (3) (Total 8 marks) Q7. Photographic film often contains silver bromide. Silver bromide is changed by light to form silver which appears as a black solid. This darkens the photographic film. A photographic film can be made by coating thin transparent plastic with a gel containing silver bromide. The main steps in making this photographic film are as follows: Step Gelatine is dissolved in warm water to make a solution. Step Step 3 Step 4 Step 5 Step 6 Step 7 Compound A, a soluble compound which contains bromide ions, is dissolved into this solution. The lights are turned out in the darkroom. Compound B, a soluble compound which contains silver ions, is dissolved in water. The solution of compound B is added to the solution containing compound A and gelatine. Solid silver bromide is formed. The warm mixture is poured onto thin, transparent plastic film. The mixture sets to form a gel containing solid silver bromide. Page of 68

13 (a) The table below gives information about the solubility of some compounds. SOLUBLE INSOLUBLE All sodium and potassium salts All nitrates Most chlorides, bromides and iodides Most sulfates Sodium, potassium and ammonium carbonates Silver and lead chlorides, bromides and iodides Lead sulfate and barium sulfate Most other carbonates Use the table to help you to name suitable compounds for A and B. Compound A... Compound B... Suggest why the lights are turned out at step 3 in this method of making a photographic film (c) What type of chemical reaction takes place when the compounds are mixed in step 5?... (d) The photographic film is placed in a camera and a picture is taken. Where light hits the photographic film the silver ions (Ag+) are changed into silver metal (Ag). Explain why this reaction is a reduction (Total 6 marks) Page 3 of 68

14 Q8. Pieces of zinc react with dilute acid to form hydrogen gas. The graph shows how the volume of hydrogen gas produced changes with time. (a) Describe, as fully as you can, how the volume of gas produced changes with time. A student wants to make the reaction take place faster. Some suggestions are given in the table. Put ticks ( ) next to the two suggestions that would make the reaction take place faster. Suggestions ( ) Use bigger pieces of zinc. Use a more concentrated acid. Use zinc powder. Decrease the temperature of the acid. (Total 4 marks) Page 4 of 68

15 Q9. Instant cold packs are used to treat sports injuries. One type of cold pack has a plastic bag containing water. Inside this bag is a smaller bag containing ammonium nitrate. The outer bag is squeezed so that the inner bag bursts. The pack is shaken and quickly gets very cold as the ammonium nitrate dissolves in the water. (a) One of the statements in the table is correct. Put a tick ( ) next to the correct statement. Statement ( ) The bag gets cold because heat energy is given out to the surroundings. The bag gets cold because heat energy is taken in from the surroundings. The bag gets cold because plastic is a good insulator. Draw a ring around the word that best describes the change when ammonium nitrate dissolves in water. electrolysis endothermic exothermic Page 5 of 68

16 (c) Suggest and explain why the pack is shaken after the inner bag has burst. (Total 4 marks) Q0. A student heated some blue copper sulphate crystals. The crystals turned into white copper sulphate. (a) The blue copper sulphate had to be heated to change it into white copper sulphate. State whether the reaction was exothermic or endothermic.... Explain your answer. The word equation for this reaction is shown below. (i) What does the symbol tell you about this reaction? Page 6 of 68

17 How could the student turn the white powder back to blue? (Total 3 marks) Q. Solutions A and B are colourless. When they are mixed, they react and turn blue after a period of time. A student investigated how temperature affected the rate of reaction between solutions A and B. The rate was measured by timing how long the mixture took to turn blue. The results are shown in the table. Temperature in C Time taken to turn blue, in seconds Page 7 of 68

18 (a) (i) Draw a graph for these results. (3) Use your graph to find how long it takes the solution to turn blue at 40 C. Time =... s (i) How does the rate of reaction change as the temperature is increased? Page 8 of 68

19 Explain, in terms of particles, why temperature has this effect on the rate of reaction. To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words. (3) (c) State one variable that must be kept constant to make this experiment a fair test. (Total 9 marks) Q. This label was on a bottle of stain remover. Page 9 of 68

20 When Simply Amazing is mixed with water a reaction takes place which produces bubbles of oxygen gas. (i) Suggest a method that you could use to measure how quickly this reaction takes place. Read the instructions on the label and then suggest how increasing the temperature of the water affects the rate of this reaction. (iii) Suggest one other way in which the rate of a reaction can be changed. (Total 4 marks) Page 0 of 68

21 Q3. A student did two experiments using ammonium chloride. (a) In the first experiment the student heated a small amount of ammonium chloride in a test tube. Two reactions take place in the test tube. Reaction ammonium chloride ammonia + hydrogen chloride (colourless gases) Reaction ammonia + hydrogen chloride ammonium chloride (i) Complete the sentences by crossing out the incorrect word in each box. Reaction takes place at a high low temperature. Reaction takes place at a high low temperature. Draw a ring around the word which best describes reactions and. combustion displacement oxidation reduction reversible (iii) Suggest a reason for the mineral wool at the top of the test tube. Page of 68

22 In the second experiment the student mixed a small amount of ammonium chloride with some water in a beaker. The temperature of the water was measured before and after adding the ammonium chloride. Temperature before adding the ammonium chloride Temperature after adding the ammonium chloride 0 C 6 C Draw a ring around the word which best describes the process which takes place. combustion displacement endothermic exothermic freezing (Total 4 marks) Q4. A student investigated some instant soup. (a) Instant soup contains a food additive which has the formula: NaH PO 4 Give the names of all the elements in this compound. The periodic table on the Data Sheet may help you to answer this question. The student investigated the reaction which takes place when soup powder is added to cold water. The student thought that the reaction might be exothermic. (i) What is meant by the term exothermic reaction? Page of 68

23 Describe an experiment that the student could do to prove that this reaction is exothermic. To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words. (4) (Total 8 marks) Q5. A student studied the reaction between dilute hydrochloric acid and an excess of calcium carbonate. calcium carbonate + hydrochloric acid calcium chloride + water + carbon dioxide The student measured the volume of carbon dioxide produced in the experiment. The results are shown on the graph. Page 3 of 68

24 (a) After how many minutes had all the acid been used up?... minutes The student wrote this conclusion for the experiment: The reaction gets slower and slower as the time increases. Explain why the reaction gets slower. Your answer should be in terms of particles. (c) A second experiment was carried out at a higher temperature. All other factors were the same. Draw a line on the graph above to show the results that you would expect. (Total 5 marks) Q6. (a) Indigestion tablets called antacids can be taken to react with excess hydrochloric acid in the stomach. A student investigated two different antacid tablets labelled X and Y. (i) Both tablets, X and Y, contained calcium carbonate. Give the chemical symbol for each of the three elements in calcium carbonate. (3) Name the gas formed when calcium carbonate reacts with hydrochloric acid. The student first reacted tablet X and then tablet Y, with 00 cm 3 of a hydrochloric acid solution. The student measured the volume of gas produced during the first five minutes. The results are shown in the table. Time in minutes Volume of gas in cm 3 Tablet X Volume of gas in cm 3 Tablet Y Page 4 of 68

25 (i) Draw a graph of the results for tablet Y. (A graph of the results for tablet X has been drawn for you.) (3) Tablet X contains less calcium carbonate than tablet Y. How do the results show this? (iii) Explain why the rate of reaction slows down for both tablets. (Total 0 marks) Q7. A student studied the effect of temperature on the rate of reaction between hydrochloric acid and sodium thiosulphate. Page 5 of 68

26 The student mixed 50 cm 3 of a sodium thiosulphate solution and 5 cm 3 of hydrochloric acid in a flask. The flask was placed over a cross. The student timed how long after mixing the cross could no longer be seen. (a) (i) Balance the chemical equation for this reaction. Na S O 3 (aq) + HCl(aq) NaCl(aq) + H O(l) + SO (g) + S(s) What causes the cross to be seen no longer? A graph of the results is shown. (i) What effect does temperature have on the rate of this reaction? Explain why temperature has this effect on the rate of reaction. (Total 5 marks) Page 6 of 68

27 H O... + O Q8. A student tried to make some magnesium sulphate. Excess magnesium was added to dilute sulphuric acid. During this reaction fizzing was observed due to the production of a gas. (i) Complete and balance the chemical equation for this reaction H SO (3) At the end of the reaction the solution remaining was filtered. Why was the solution filtered? (iii) The filtered solution was left in a warm place. Explain why the filtered solution was left in a warm place. (Total 6 marks) Q9. This question is about rates of reaction. (a) Hydrogen peroxide (H O ) decomposes very slowly at room temperature. (i) Complete the balanced chemical equation for this reaction by writing in the formula of the missing product. The decomposition is much faster if manganese oxide is mixed with the hydrogen peroxide. Complete the sentence. Manganese oxide acts as a... for decomposition of hydrogen peroxide. Page 7 of 68

28 In an experiment g of manganese oxide was mixed with 50 cm 3 of hydrogen peroxide solution. The results show the volume of oxygen collected during six minutes. Time in minutes Volume of oxygen in cm (i) Draw a graph of these results. (3) How long did it take for the decomposition to stop? Page 8 of 68

29 (iii) Why did the decomposition stop? (c) In a second experiment water had been added to the hydrogen peroxide solution. Again 50 cm 3 of this hydrogen peroxide solution was mixed with g of manganese oxide. (i) For this second experiment, sketch, on the same grid, a graph line you would expect to get. In this second experiment, why would the rate of reaction be different to the first experiment? (Total 0 marks) Q0. Calcium tablets are taken to build and maintain strong bones and teeth. (a) These tablets react with hydrochloric acid in the stomach. CaCO 3 ( ) + HCl(aq) CaCl ( ) + H O( ) + CO ( ) (i) Add all these missing state symbols to the balanced chemical equation. The calcium salt that is formed is absorbed during digestion. What is the name of the calcium salt? Page 9 of 68

30 The volume of carbon dioxide produced by one calcium tablet in the stomach can be found as shown. The volume of carbon dioxide was recorded every 30 seconds until the reaction stopped. Time in seconds Volume of gas in cm (i) Complete the graph of these results. (3) Describe one way in which this reaction can be made to go faster. Page 30 of 68

31 (iii) A calculation, using the mass of this tablet, showed that 80 cm 3 of carbon dioxide would be produced if the tablet was pure calcium carbonate. What do the results show about the purity of the tablet? Explain your answer by calculating the purity of this tablet. (3) (Total 0 marks) Q. Calcium carbonate reacts with dilute hydrochloric acid as shown in the equation below. CaCO 3 (s) + HCl(aq) CaCl (aq) + H O(l) + CO (g) The rate at which this reaction takes place can be studied by measuring the amount of carbon dioxide gas produced. The graph below shows the results of four experiments, to 4. In each experiment the amount of calcium carbonate, the volume of acid and the concentration of the acid were kept the same but the temperature of the acid was changed each time. The calcium carbonate was in the form of small lumps of marble. Page 3 of 68

32 (a) Apart from altering the temperature, suggest two ways in which the reaction of calcium carbonate and hydrochloric acid could be speeded up Which graph, to 4, shows the results of the experiment in which the acid had the highest temperature? Experiment... Explain fully how you know. (c) (i) In experiment, how does the rate of reaction after one minute compare with the rate of reaction after two minutes? Explain, as fully as you can, why the reaction rate changes during experiment. (Total 7 marks) Q. The word equation below shows a reaction used in an industrial process. chromium oxide + aluminium chromium + aluminium oxide The reaction is highly exothermic. (a) What is an exothermic reaction? Page 3 of 68

33 Name the products of this reaction. (c) In the reaction one substance is reduced. (i) Name the substance which is reduced. What happens to the substance when it is reduced? (Total 5 marks) Q3. This item appeared in the Wolverhampton Express and Star on October 3st, 997. Read the passage and answer the questions that follow. Fumes scare at factory Workers were forced to flee a factory after a chemical alert. The building was evacuated when a toxic gas filled the factory. It happened when nitric acid spilled on to the floor and mixed with magnesium metal powder. (a) The equation which represents the reaction between magnesium and nitric acid is: Mg (s) + 4HNO 3(aq) Mg(NO 3 ) (aq) + H O + NO (g) Give the formula of the toxic gas that was produced.... Explain, in terms of particles, how the toxic gas was able to fill the factory quickly Page 33 of 68

34 (c) The reaction of nitric acid with magnesium metal powder is more dangerous than if the acid had fallen on to the same mass of magnesium bars. Explain why (d) (i) Water was sprayed on to the magnesium and nitric acid to slow down the reaction. Explain, in terms of particles, why the reaction would slow down. Explain why it is better to add alkali, rather than just add water to the spillage. (Total 7 marks) Q4. Hydrogen peroxide (H O ) contains the same elements as water (H O). (a) Name the hazard symbol shown by using the correct word from the box. corrosive flammable oxidising toxic Hydrogen peroxide decomposes in the presence of a catalyst. H O (aq) H O(l) + O (g) (i) Complete the word equation for this chemical reaction. hydrogen peroxide water +... Page 34 of 68

35 What does a catalyst do to a chemical reaction? (Total 3 marks) Q5. Marble is a rock that contains mainly calcium carbonate. This reacts with hydrochloric acid. calcium carbonate + hydrochloric acid calcium chloride + water + carbon dioxide The rate of this reaction was followed by measuring the mass of carbon dioxide formed. Two 0 g samples of marble, A and B, were each reacted with 50 cm 3 of dilute hydrochloric acid, at different temperatures. The mass of carbon dioxide formed in each reaction was recorded and plotted to produce the graph below. Each reaction stopped when no more carbon dioxide was formed. In both experiments some marble was left unreacted when the reaction stopped. Page 35 of 68

36 (a) Explain how you can tell which sample, A or B, reacted faster with the dilute hydrochloric acid. The faster rate of reaction was caused by using a higher temperature. Explain, in terms of particles, why a higher temperature causes a faster rate of reaction. (3) (Total 5 marks) Q6. Hydrogen peroxide slowly decomposes into water and oxygen. hydrogen peroxide water + oxygen The reaction can be speeded up by adding manganese dioxide. (a) (i) What do we call a substance that speeds up a chemical reaction without being changed itself? Give two other ways of increasing the rate of this reaction Page 36 of 68

37 The diagram shows how the rate of this reaction can be measured. As the hydrogen peroxide decomposes, the mass of the flask and its contents decreases. Why does this decrease in mass take place? (Total 4 marks) Q7. Magnesium reacts with dilute sulphuric acid. magnesium + sulphuric acid magnesium sulphate + hydrogen A student measured the volume of hydrogen given off every 0 seconds. The results are shown on the graph. Page 37 of 68

38 (a) The average rate of hydrogen production in the first 0 seconds is (60 cm 3 0 s) = 6 cm 3 /s. (i) Calculate the average rate of production of hydrogen between 30 seconds and 50 seconds. Show clearly how you work out your answer. Rate... cm 3 /s (3) Explain, as fully as you can, why the average rate between 30 and 50 seconds is different from the rate between 0 and 0 seconds. In industry, enzymes are used in both batch processes and continuous processes. Give one reason why continuous processes are usually more profitable than batch processes. (Total 6 marks) Page 38 of 68

39 Q8. Many indigestion tablets contain calcium carbonate as their only active ingredient. Calcium carbonate neutralises some of the hydrochloric acid in the stomach. Two different indigestion tablets, X and Y, were separately reacted with excess hydrochloric acid. The volume of gas given off in each reaction was measured every minute. The results are shown in the graph. (i) Which tablet, X or Y, contained most calcium carbonate?... Explain the reason for your answer. Which tablet, X or Y, reacted faster with hydrochloric acid?... Explain the reason for your answer. Page 39 of 68

40 Zn + HCl ZnC + H (iii) Explain the shape of the graph for tablet X between 3 and 5 minutes. (Total 3 marks) Q9. Zinc powder normally reacts slowly with hydrochloric acid. (a) Balance the symbol equation for the reaction. The graph shows the results from a reaction of.0 g of zinc powder with 0 cm 3 of dilute hydrochloric acid. It gives off a gas and forms zinc chloride, ZnCl. Some unreacted zinc is left at the end. Copper powder is a good catalyst for the reaction of zinc with hydrochloric acid. (i) A mixture of 0 cm 3 of the same dilute hydrochloric acid and.0 g of copper powder was added to.0 g of zinc powder. What is the maximum volume of gas which could be given off?... cm 3 Page 40 of 68

41 (iii) Draw a graph, on the axes above, for an experiment where 0 cm 3 of the same dilute hydrochloric acid was added to.0 g of copper powder mixed with.0 g of zinc powder. Give two other ways the reaction described in part (i) could be made to go faster (c) Copper powder can be formed by adding copper sulphate solution to the mixture of zinc powder and acid. (i) Why does zinc react with copper sulphate solution to produce copper? Write the word equation for the reaction. (Total 8 marks) Page 4 of 68

42 Q30. The graph shows the volume of gas given off during an experiment using hydrogen peroxide solution and manganese oxide. Draw, on the axes above, a graph to show the result you would expect if the volume of hydrogen peroxide solution had been the same, but it was twice as concentrated. (Total 3 marks) Q3. The apparatus shown in the diagram was used to investigate the rate of reaction of excess marble chips with dilute hydrochloric acid, HCl. Marble is calcium carbonate, formula CaCO 3. The salt formed is calcium chloride, CaCl. (a) Write a balanced equation for the reaction Page 4 of 68

43 The following results were obtained from the experiment. Time in minutes Reading on balance in g (i) Plot the results and draw a graph on the axes below. (3) Continue the graph you have drawn to show the expected reading after minutes. (iii) On the axes above, sketch a graph of the result which would be obtained if in a similar experiment the same mass of powdered marble was used instead of marble chips. (Total 8 marks) Page 43 of 68

44 Q3. Marble chips (calcium carbonate) react with dilute hydrochloric acid. calcium + hydrochloric calcium + carbon + water carbonate acid chloride dioxide A student wanted to find out if the size of the marble chips made a difference to how fast the reaction took place. (a) What readings should she take? She repeated the experiment but this time used the same mass (0g) of large marble chips. In both experiments there was some marble left in the flask when the reaction stopped. These are the results of the two experiments. TIME (minutes) Loss in mass (g), using small chips Loss in mass (g), using large chips (i) Explain the loss in mass in the two experiments. Page 44 of 68

45 What difference does the size of the chips make? (c) A chemical reaction occurs when reacting particles collide with sufficient energy. The reaction between marble and hydrochloric acid is faster if the acid is at a higher temperature. Explain why. (3) (Total 7 marks) Q33. A student does an experiment to examine the rate of reaction between magnesium and dilute hydrochloric acid. She adds 5 cm³ of the acid to a weighed amount of the metal. The reaction produces hydrogen gas. Magnesium + hydrochloric acid magnesium + hydrogen chloride She collects the gas and measures the volume collected at one minute intervals. All the metal reacted but there was some acid left unreacted. Her results are shown on the graph. Page 45 of 68

46 (a) The diagram shows part of the apparatus she used for the experiment. Complete the diagram to show how the student could collect the hydrogen produced and measure the volume after each minute. (i) When is the rate of reaction at its fastest? State one way in which she could increase the rate of reaction. (c) (i) What is the total volume of hydrogen collected in the experiment?... cm³ State one way in which she could increase the final volume of hydrogen collected. (Total 6 marks) Page 46 of 68

47 M. (a) (i) curve missing anomalous point answer in the range of to 00.5 (iii) reaction goes quickly at first accept reaction slows down reaction stops because carbon dioxide is produced accept gas is produced carbon dioxide / gas escapes, therefore the mass of the flask and contents decreases (c) (i) balance B because during the experiment a gas / carbon dioxide escapes from the flask therefore the balance needs a high resolution to measure the small changes in the mass (d) the (marble) powder has a larger surface area than the (marble) chips therefore there would be more collisions with the acid particles (within the same amount of time) [] M. (a) (i) column mass spectrometer (i) 65 if answer is not correct then evidence of correct working gains one mark. e.g. (0 ) Page 47 of 68

48 0.37% accept 0 / 0.4 / if answer is not correct then evidence of correct working gains one mark. e.g. minimum evidence would be 4/35 (c) any two from: faster more accurate (d) detects smaller amounts to avoid bias accept to check / compare the result to improve reliability [0] M3. (a) water accept H O or 5H O (c) must be below halfway the cold water / ice / cubes (owtte) accept cooled down or references to cold reversible reaction (d) (i) 0.87g the student made errors in weighing during the experiments the student did not heat the copper sulfate for long enough in one of the experiments Page 48 of 68

49 (e) white blue allow mark for blue to white [8] M4. (a) carbon dioxide must be name do not accept carbon oxide (i) the temperature of the solution will decrease (list principle) energy is taken in from the surroundings (list principle) [3] M5. (a) (i) gives out a large amount of energy only water produced / product is non polluting (owtte) allow it does not harm the environment does not explode / burst into flames owtte ignore will not react (iii) hydrogen absorbed and released much faster allow more efficient allow can store a larger amount (i) B (iii) a lithium atom loses an electron C Page 49 of 68

50 (c) reversible (d) (i) much smaller surface area [0] M6. (a) sensible line of best fit which goes through or close to all the points except the anomalous point allow wobbly / short double lines ± ½ square loss of gas / loss of CO idea of gas produced / formed (c) 7 (d) (i) steeper line from around the same starting point and left of the points allow crosses if they are fully correct for mark levelling off at 99 accept short level line at 99 ± ½ square Page 50 of 68

51 any three from: particles / molecules / atoms/ ions have more energy allow given / gain / get energy move faster ignore move about more ignore vibrate more / faster collide more often or more chance of collisions or bump into each other more ignore collide quicker / faster collide with more force / energy or more particles have the activation energy or more collisions result in reaction or more collisions are successful 3 [8] M7. (a) Compound A any one from: sodium bromide accept correct formulae potassium bromide ammonium bromide hydrogen bromide any metal bromide except silver and lead. Compound B silver nitrate accept silver sulphate the silver compound will decompose / silver ions be reduced to silver (owtte) accept film would darken owtte accept any idea of light changing silver bromide / silver ions / silver nitrate / silver sulphate allow forms a black solid / it would turn black Page 5 of 68

52 (c) (d) precipitation accept descriptions of precipitation reactions accept double decomposition accept precipitate do not allow displacement electrons are gained the second mark must be linked to electrons accept it / silver / silver ions gains electrons for both marks ignore references to oxygen [6] M8. (a) any two from: increases owtte allow goes up until reaches maximum / levels off owtte quickly at first owtte then more slowly / rate decreases allow reaction finished ignore rate increases use a more concentrated acid list principle applies use zinc powder [4] M9. (a) the bag gets cold because heat energy is taken in from the surroundings endothermic Page 5 of 68

53 (c) any two from: mix / spread (the ammonium nitrate and water) dissolve faster(*) get cold faster or so the whole bag gets cold(*) (*)allow increase rate or quicker reaction particles collide more or more collisions [4] M0. (a) endothermic and because it takes in heat / energy both for one mark (i) reversible reaction (or explanation) add water do not accept cooling or reverse the reaction [3] M. (a) (i) accurate plotting of points ( square) marks for all points mark for 3 or 4 points sensible smooth curve reasonable attempt do not accept double lines or dot to dot accurately read from their graph to square (i) (as temperature increases) rate increases accept speeds up, gets faster, gets quicker accept higher speed do not accept gets bigger / higher unqualified do not accept answers about time on its own Page 53 of 68

54 Quality of Written Communication The answer to this question requires ideas in good English in a sensible order with correct use of scientific terms. Quality of written communication should be considered in crediting points in the mark scheme. maximum marks if ideas not expressed well any three from: for converse maximum marks particles have more energy higher kinetic energy particles move faster do not accept move more or vibrate more 3 more collisions accept greater rate of collisions more energetic / successful / harder collisions more particles have activation energy (c) concentration (of solutions) or volume (of solutions) accept how much of accept references to intensity of colour accept same endpoint accept rate of stirring / shaking do not accept reference to solids or catalysts etc ignore containers do not accept ph [9] M. (i) measure volume / mass of gas produced in a certain time period mark is for a sensible way of measuring the amount of product produced and mark is for the idea of timing e.g. measure volume of gas produced at regular time intervals or time taken to fill a test tube with the gas or collect a certain volume of gas (measuring the rate at which bubbles are produced e.g. number of bubbles in 30 seconds gains only mark unless an enclosed system is used) or measure decrease in mass of flask and contents at regular time intervals or time taken for the mass to decrease by certain amount Page 54 of 68

55 increases rate (owtte) change the concentration or add a catalyst or change the surface area or lower the temperature accept expose to sunlight (owtte) or change the amount of water / powder / solution used ignore stirring [4] M3. (a) (i) high and low both needed for mark (iii) reversible to prevent ammonium chloride / solid / particles escaping idea of a filter do not accept to prevent gases escaping endothermic [4] M4. (a) sodium hydrogen phosphorus oxygen marks for all 4 mark for or 3 0 marks for 0 or not symbols / formulae Page 55 of 68

56 (i) gives out gets hot(ter) / temperature rises heat / energy independent mark Quality of written communication for clearly expressed ideas take temperature of water at start owtte take temperature after adding soup powder plus any one from: using a thermometer mix / stir / shake etc in beaker / conical flask / test tube / plastic cup temperature will rise (indicates an exothermic reaction) [8] M5. (a) 6 accept hydrochloric acid used up / reacted / combined / or fewer particles (of hydrochloric acid) or fewer hydrogen ions owtte accept reactants used up accept less calcium carbonate or smaller surface area of calcium carbonate accept lower concentration / less crowded do not accept atoms / molecules ignore references to energy do not accept references to atoms or molecules fewer collisions owtte independent mark Page 56 of 68

57 CaCO 3 = marks O not O (c) steeper curve initially independent marks levels out at same volume must indicate levelling out if line goes higher than 66 do not award this mark diagonal line only = 0 marks if steeper initially and then crosses the line and finishes correctly, then loses one [5] M6. (a) (i) must be chemical symbol Ca C carbon dioxide must be name (i) points all correct marks one point incorrect mark two points incorrect 0 marks suitable line -narrow neat single curve not dot to dot reaction with X forms less gas must include X or Y do not penalise for H /O if (a) already penalised do not accept is finished in less time or slower/faster reaction or lower on graph Page 57 of 68

58 (iii) any two from: concentration (of acid) decreases/less reacting particles/molecules not acid/caco 3 runs out/is used up surface area of calcium carbonate decreases not strength of acid decreases less collisions between reacting particles not smaller (amount of) CaCO 3 [0] M7. (a) (i) Na S O 3 (aq) + HCl(aq) NaCl(aq) + H O(l) + S(s) + SO (g) (formation of) sulphur accept precipitate or solid produced do not accept goes cloudy or milky (i) heat temperature increased temperature increases (the rate of reaction) or decreased temperature decreases rate of reaction may be gained in part if stated and not implied (these ideas may be given in (i)) particles have more kinetic energy accept particles move faster more collisions (so more reactions) more energetic collisions two marks [5] M8. (i) Mg + (H SO 4 ) MgSO4 + H deduct mark if not balanced only if all three correct accept alternative metal of similar reactivity for example Zn or Fe candidate would not then be awarded first mark for Mg then error carried forward deduct mark if not balanced only if all three correct Page 58 of 68

59 to remove the (excess) magnesium accept separate accept insoluble substances or solids or residue do not accept unreactive substances or impurities or remove magnesium from sulphuric acid (iii) to evaporate (some of the water or solution) to form crystals or crystallise accept to form a saturated solution or concentrated solution do not accept to leave MgSO 4 [6] M9. (a) (i) H O must be formula catalyst (i) correct plotting mark deducted per error to a maximum of do not accept a complete dot-to-dot line do not accept a bar chart if the (0,0) point is missing and line to one minute missing then maximum mark is best fit single line if curve correct but no obvious points award 3marks no units required Page 59 of 68

60 (iii) all hydrogen peroxide had reacted accept all hydrogen peroxide had decomposed or been used up accept no hydrogen peroxide (particles) left (c) (i) remains lower than previous line do not accept bar chart line levels off lower than 60cm 3 correct points but no line drawn then maximum mark decrease of (hydrogen peroxide) concentration accept concentration is less accept fewer collisions (of particles) do not accept weaker solutions or dilute solutions [0] M0. (a) (i) (s) (aq) (g) or 3 correct mark correct 0 marks calcium chloride (i) points deduct mark for each error to a maximum of marks line accept a single line best fit curve accept reasonable attempt at curve (iii) increase temperature or heat accept increase surface area or increase concentration or description 75% or ¾ not pure mark only 60 cm 3 (instead of 80 cm 3 of gas) or 00 mark 3 [0] Page 60 of 68

61 M. (a) increase concentration of acid; increase surface area of solid or grind up the solid; add a catalyst any two for mark each ; it is the one that makes the gas fastest (steeper curve etc) (second part is dependant on first) for mark each (c) (i) faster after one minute, slower after minutes for mark the reactants get used up; so concentration decreases/less chance of collision for mark each [7] M. (a) gives out heat each for mark chromium and aluminium oxide (c) (i) chromium oxide oxygen removed/gains electrons [5] M3. (a) NO / NO (g) / Nitrogen dioxide for one mark particles of gas move / they move reject spread out particles move randomly / mix / go between air molecules / diffusion any two for mark each Page 6 of 68

62 (c) faster reaction / more surface area (not smaller pieces) for one mark (d) (i) either lower temperature / particles move slower fewer collisions (owtte) / less energetic collisions / owtte or acid diluted (owtte) fewer collisions (owtte) for mark each alkali neutralises the acid / stops the reaction or water will only slow the reaction not stop it either for mark [7] M4. (a) oxidising (i) oxygen ignore any numbers (catalyst) speeds up a (chemical reaction) accept changes the rate (of reaction) [3] M5. (a) A faster because: the graph line steeper / the reaction had stopped earlier accept sample B slower because: the graph line was less steep / the reaction stopped later A because CO given off faster / fizzes more for mark B because CO given off slower / fizzes less for mark increases the speed / energy of the (hydrochloric acid) particles collide more frequently collide more energetically / successfully accept more successful collisions = marks [5] Page 6 of 68

63 M6. (a) (i) catalyst / enzyme any two from do not accept increase volume of peroxide heat stir / shake increase concentration of peroxide / catalyst oxygen lost do not allow incorrect gas [4] M7. (a) (i).5 correct answer gains three marks if incorrect allow mark for correct readings (30 and 75) and further mark for 45 0 allow e.c.f. 3 concentration of reactant(s) lower fewer collisions per second / time unit labour costs lower / enzymes costs lower not stop and start [6] M8. (i) (Y) more gas / carbon dioxide given off (X) curve / slope steeper accept rises more rapidly / only took 30 seconds Page 63 of 68

64 M9. (a) Zn + HC ZnC + H (iii) (flat) since calcium carbonate / substrate all used up accept the reaction has stopped / no more gas is being produced [3] (i).5 (iii) steeper curve same volume of gas evolved do not credit two intersects of straight lines accept a sharp bend any two from: stir it accept mix it better heat it accept warm it use a more finely divided catalyst accept use a better catalyst or more finely divided zinc do not credit use acid of a higher (c) (i) any one from zinc is more reactive than copper accept zinc is above copper in the reactivity series zinc displaces copper accept it is higher than copper in the reactivity series zinc + copper sulphate copper + zinc sulphate ignore the presence of acid or water accept a balanced equation [8] Page 64 of 68

65 M30. graph steeper becomes horizontal reaches twice the height_, 40 cm 3 cm 3 [3] M3. (a) CaCO 3 + HC CaC + CO + H O one mark for CO and H O or H CO 3 one mark for balancing the equation (i) linear suitable scale for y axis ± one small square accurate plots deduct one mark for each error plot smooth curve through the points or a line of best fit this mark requires a neat smooth curve curve becomes almost horizontal at or above 68.5 do not credit a straight line reaching 68.5 at mins accept a plot at 68.6 (iii) steeper initial part to curve becoming nearly horizontal between 68.6 and 68.4 g [8] Page 65 of 68

66 M3. (a) ideas that ref to read the balance / read the mass / weight ref to read the stop clock / read the time readings taken at the beginning and end / at regular intervals for mark each (i) loss of carbon dioxide (from the flask) } smaller chips give faster reaction / reaction } mark as a whole finishes quicker /dissolved faster [or reverse] } smaller chips have a larger surface area } any for mark each [Allow converse answers] (c) ideas that heating increases the speed / energy / vibration of the (acid) particles / marble particles (acid) particles collide (with marble chips / (particles)) more frequently / more likely to collide reacting particles collide with greater energy / collide faster so particles more likely to react [do not accept react faster ] [Accept atoms, molecules or ions instead of particles in this question] any three for mark each 3 [7] Page 66 of 68

67 M33. (a) (must be possible for the gas to enter and displace the water) or other suitable apparatus apparatus to collect the gas correctly assembled for mark calibrated collection vessel (award even if diagram is wrong) for mark (i) at the start / in the first / minutes (or any time within this range) for mark increase the temperature / use smaller pieces of metal / use more metal / increase the surface area of the metal / add a catalyst / shake the flask / increase the concentration / strength of the acid for mark (c) (i) 48 for mark increase the amount of magnesium used for mark (do not allow increase the amount of acid used) [6] Page 67 of 68

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