C6 Rate and Extent of Chemical Change

Transcription

1 C6 Rate and Extent of Chemical Change 35 Questions Name: Class: Date: Time: Marks: Comments: Page of

2 A student investigated the rate of the reaction between magnesium and dilute hydrochloric acid. The student used the apparatus shown in Figure to collect the gas produced. Figure (a) Outline a plan to investigate how the rate of this reaction changed when the concentration of the hydrochloric acid was changed. Describe how you would do the investigation and the measurements you would make. Describe how you would make it a fair test. You do not need to write about safety precautions. (6) Page 2 of

3 (b) Figure 2 shows the gas syringe during one of the experiments. Figure 2 What is the volume of gas collected? Tick one box. 5.3 cm cm cm cm 3 () Page 3 of

4 (c) Figure 3 shows the student s results for one concentration of hydrochloric acid. Figure 3 The table below shows the student s results when the concentration was two times greater than the results on Figure 3 Time in seconds Volume of gas produced in cm Plot the results in the table above on the grid in Figure 3. Draw a line of best fit. (3) Page 4 of

5 (d) Give one conclusion about how the rate of reaction changed when the concentration of hydrochloric acid was changed. () (Total marks) 2 Sulfur dioxide (SO 2 ) is used to manufacture sulfuric acid. (a) Explain why sulfur dioxide has a low boiling point. (3) (b) The equation shows one stage in the manufacture of sulfuric acid from sulfur dioxide. 2SO 2 (g) + O 2 (g) 2SO 3 (g) The reaction is exothermic in the forward direction. Use Le Chatelier s Principle to predict the effect of increasing the temperature on the amount of sulfur trioxide (SO 3 ) produced at equilibrium. Give a reason for your answer. (c) Use Le Chatelier s Principle to predict the effect of increasing the pressure on the amount of sulfur trioxide (SO 3 ) produced at equilibrium. Give a reason for your answer. (Total 7 marks) Page 5 of

6 3 The rate of chemical reactions can be changed by changing the conditions. (a) Methane burns in oxygen to produce carbon dioxide and water. The activation energy for the reaction is 2648 kj / mol. The reaction gives out 88 kj / mol of energy. The figure below shows the reaction profile for this reaction. Complete the reaction profile. Draw arrows to represent: the activation energy the energy given out. (4) (b) What percentage of the activation energy is the energy given out? () (c) Calcium carbonate decomposes when it is heated: The decomposition of calcium carbonate is an endothermic reaction. How would the reaction profile for decomposition of calcium carbonate be different from the reaction profile of methane burning in oxygen? () Page 6 of

7 (d) Catalysts are used in chemical reactions in industry. Give two properties of catalysts. For each property, explain why it makes the catalyst useful in industry. (4) (e) Enzymes are biological catalysts. What type of molecule is an enzyme? Tick one box. Carbohydrate Hydrocarbon Lipid Protein () (f) If enzymes are denatured they stop working. Give two ways an enzyme can be denatured.. 2. Page 7 of

8 (g) An enzyme called lactase catalyses the reaction that breaks down lactose to smaller molecules. One model used to explain how enzymes affect reactions is called the lock and key model. Use the lock and key model to explain why lactase cannot be used to speed up all chemical reactions. (3) (Total 6 marks) Page 8 of

9 4 Ammonium nitrate (NH 4 NO 3 ) is produced by reacting ammonia with nitric acid. A student measured the mass of ammonium nitrate that dissolves in 00 cm 3 of water at different temperatures. The table below shows the student s results. Temperature in C Mass of ammonium nitrate in g that dissolves in 00 cm 3 water (a) Use the table above to plot a graph of the solubility of ammonium nitrate on the figure below. Page 9 of

10 (4) (b) At 20 C, 90 g of ammonium nitrate dissolves in 00 cm 3 of water. Calculate the amount of ammonium nitrate (in moles) that dissolves in dm 3 of water at 20 C. Relative atomic masses (A r ): H = ; N = 4; O = 6 Amount of dissolved ammonium nitrate = mol (3) (c) Farmers use ammonium nitrate as a fertiliser. Farmers want to slow down the rate at which ammonium nitrate fertiliser dissolves in the water in the soil. Suggest why they spread the fertiliser in the form of small beads instead of a fine powder. Page 0 of

11 (d) Ammonia is needed to make ammonium nitrate. The reaction used to make ammonia is: N 2 (g) + 3H 2 (g) 2NH 3 (g) The forward reaction is exothermic. At equilibrium, about 35% of the nitrogen and hydrogen are converted to ammonia at 450 C and 200 atmospheres pressure. Explain the effects of increasing the temperature, or increasing the pressure, on the amount of ammonia produced at equilibrium. (4) (Total 3 marks) 5 A student investigates how the concentration of an acid affects the rate of a reaction. This is the method used.. Put a 3 cm piece of magnesium ribbon into a conical flask. 2. Add 50 cm 3 of 0.5 mol / dm 3 hydrochloric acid to the flask. 3. Collect and measure the volume of gas produced at 0 second intervals. 4. Repeat with different concentrations of hydrochloric acid using the same length of magnesium ribbon and volume of acid. Page of

12 The student s results are shown in the figure below. (a) How do the results show that increasing the concentration of acid increases the rate of reaction? You must use data from the graph in your answer. Page 2 of

13 (b) Explain why the rate of reaction changes as the concentration of the acid increases. You should answer in terms of particles. (3) (c) Student A said that the final volume of gas collected was lower for a concentration of 0.5 mol dm 3 because the reaction had not finished. Student B said it was because all the acid had reacted. Describe further experimental work the students could do to find out which student was correct. (Total 7 marks) Page 3 of

14 6 Amylase catalyses the breakdown of starch into sugars. A student investigated the effect of amylase on the reaction at different temperatures. Figure shows the apparatus the student used. Figure This is the method used.. Put starch suspension into a test tube. 2. Add amylase solution. 3. Put the test tube in a beaker of water at 5 C. 4. Remove a small sample of the mixture every 30 seconds and put in a spotting tile. 5. Test the sample for starch. 6. Time how long it takes to break down all of the starch in the mixture. 7. Repeat steps 5 at 20 C, 25 C and 30 C. 8. Repeat for each temperature twice more. Page 4 of

15 The table below shows the student s results. Time taken until there was no starch in the sample in minutes Temperature in C Test Test 2 Test 3 Mean (a) One of the results in the table above is anomalous. Draw a ring around the anomalous result. () (b) Calculate the mean for 30 C. () Page 5 of

16 (c) Figure 2 shows a graph of the student s results. Figure 2 Use the graph to predict how long it would take to break down all of the starch at 0 C. Time = minutes () (d) The student tested samples of the mixture for starch every 30 seconds. In each test she added one drop of iodine to the sample in the spotting tile. Predict the colour of the samples from the 20 C test at 4.0 minutes and 7.0 minutes. Colour at 4.0 minutes Colour at 7.0 minutes Page 6 of

17 (e) The student did a fourth test at 30 C. In this test the starch did not break down, even after 45 minutes. Why did the amylase not break down the starch in this test? Tick one box. The amylase solution and the starch suspension were mixed before the start of the experiment. The amylase solution had been prepared with water at 95 C. The amylase solution had been prepared with water at 20 C. The amylase solution had been stored in the fridge. () (f) The student made the following conclusion about the optimum temperature for amylase to work at. Amylase works fastest at 40 C Her teacher said that this is not a valid conclusion from her results. Describe how the student could change her method to give results that would improve the validity of her conclusion. (6) (Total 2 marks) Page 7 of

18 7 A student investigated the rate of reaction between sodium thiosulfate solution and dilute hydrochloric acid, as shown in Figure. The reaction produced a precipitate, which made the mixture turn cloudy. The student timed how long it took until she could no longer see the cross. She calculated the rate of the reaction. (a) The equation for the reaction is: Na 2 S 2 O 3 (aq) + 2 HCl(aq) 2 NaCl(aq) + S(s) + SO 2 (g) + H 2 O(l) Name the product that made the mixture go cloudy. () Page 8 of

19 (b) The student investigated the effect of changing the temperature of the sodium thiosulfate solution on the rate of reaction. She plotted her results on a graph, as shown in Figure 2. Describe the trends shown in the student s results. Page 9 of

20 (c) The student then investigated the effect of changing the concentration of sodium thiosulfate solution on the rate of the reaction. (i) Suggest two variables the student would need to control to make sure that her results were valid. From this investigation the student correctly concluded: As the concentration of sodium thiosulfate solution doubles, the rate of reaction doubles. Explain the student s conclusion in terms of particles. (3) (Total 8 marks) Page 20 of

21 8 A student investigated the rate of reaction between calcium carbonate (marble chips) and hydrochloric acid. The student used the apparatus shown in Figure. The student: recorded the volume of gas collected every 5 seconds repeated the experiment using hydrochloric acid at different temperatures. The equation for the reaction is: CaCO 3 (s) + 2 HCl(aq) CaCl 2 (aq) + H 2 O(l) + CO 2 (g) Page 2 of

22 (a) The student plotted results for the hydrochloric acid at 20 C and 40 C on a graph. Figure 2 shows the student s graph. Use information from Figure 2 to answer these questions. (i) State one conclusion the student could make about the effect of temperature on the rate of the reaction. () Give one reason why the student could make this conclusion. () (iii) For the hydrochloric acid at 60 C the student had collected 30 cm 3 after 5 seconds. Calculate the average rate of reaction from 0 to 5 seconds. Rate of reaction = cm 3 per second () Page 22 of

23 (b) The student then investigated how the surface area of marble chips affected the rate of reaction. (i) Which two variables should the student keep constant? Tick ( ) two boxes. Amount of water in the trough Concentration of acid Mass of marble chips Size of marble chips Volume of measuring cylinder Explain, in terms of particles and collisions, the effect that increasing the surface area of the marble chips has on the rate of reaction. (c) Calcium carbonate is a catalyst for the industrial production of biodiesel. Give one reason why using a catalyst reduces costs. () (Total 8 marks) Page 23 of

24 9 Hydrogen gas is produced by the reaction of methane and steam. (a) The diagram represents a molecule of hydrogen. (i) What type of bond joins the atoms of hydrogen? Tick ( ) one box. Covalent Metallic Ionic () A catalyst is used in the reaction. Draw a ring around the correct answer to complete the sentence. A catalyst increases the rate of reaction. increases the temperature. increases the yield of a reaction. () (b) The equation for the reaction of methane and steam is: CH 4 (g) + H 2 O(g) CO(g) + 3H 2 (g) (i) What is meant by the symbol? () Page 24 of

25 Lowering the pressure reduces the rate of reaction. Explain why, in terms of particles. (iii) The graph shows the yield of hydrogen at different temperatures. Temperature in C The forward reaction is endothermic. How does the graph show that the forward reaction is endothermic? () (iv) Why is a higher yield produced if the reaction is repeated at a lower pressure? () Page 25 of

26 (c) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Car engines are being developed that use hydrogen gas as a fuel instead of petrol. The table compares the two fuels. Hydrogen Petrol Energy 5700 kj per litre kj per litre State Gas Liquid Equation for combustion 2H 2 + O 2 2H 2 O 2C 8 H O 2 6CO 2 + 8H 2 O How the fuel is obtained Most hydrogen is produced from coal, oil or natural gas. Hydrogen can be produced by the electrolysis of water or the solar decomposition of water. Fractional distillation of crude oil. Page 26 of

27 Use the information in the table and your knowledge of fuels to evaluate the use of hydrogen instead of petrol as a fuel. You should describe the advantages and disadvantages of using hydrogen instead of petrol. Extra space (6) (Total 3 marks) 0 Some students were investigating the rate at which carbon dioxide gas is produced when metal carbonates react with an acid. One student reacted.00 g of calcium carbonate with 50 cm 3, an excess, of dilute hydrochloric acid. The apparatus used is shown in Diagram. Page 27 of

28 Diagram (a) (b) Dilute hydrochloric acid Complete the two labels for the apparatus on the diagram. The student measured the volume of gas collected every 30 seconds. The table shows the student s results. Time in seconds Volume of carbon dioxide collected in cm Page 28 of

29 Volume of gas = cm 3 () (i) Diagram 2 shows what the student saw at 60 seconds. Diagram 2 What is the volume of gas collected? Why did the volume of gas stop changing after 20 seconds? () (c) Another student placed a conical flask containing.00 g of a Group carbonate (M 2 CO 3 ) on a balance. He then added 50 cm 3, an excess, of dilute hydrochloric acid to the flask and measured the mass of carbon dioxide given off. The equation for the reaction is: M 2 CO 3 + 2HCl 2MCl + H 2 O + CO 2 The final mass of carbon dioxide given off was 0.32 g. (i) Calculate the amount, in moles, of carbon dioxide in 0.32 g carbon dioxide. Relative atomic masses (A r ): C = 2; O = 6 Moles of carbon dioxide = moles Page 29 of

30 How many moles of the metal carbonate are needed to make this number of moles of carbon dioxide? Moles of metal carbonate = moles () (iii) The mass of metal carbonate used was.00 g. Use this information, and your answer to part (c), to calculate the relative formula mass (M r ) of the metal carbonate. If you could not answer part (c), use as the number of moles of metal carbonate. This is not the answer to part (c). Relative formula mass (M r ) of metal carbonate = () (iv) Use your answer to part (c) (iii) to calculate the relative atomic mass (A r ) of the metal in the metal carbonate (M 2 CO 3 ) and so identify the Group metal in the metal carbonate. If you could not answer part (c) (iii), use 230 as the relative formula mass of the metal carbonate. This is not the answer to part (c) (iii). To gain full marks, you must show your working. Relative atomic mass of metal is Identity of metal (3) Page 30 of

31 (d) Two other students repeated the experiment in part (c). (i) When the first student did the experiment some acid sprayed out of the flask as the metal carbonate reacted. Explain the effect this mistake would have on the calculated relative atomic mass of the metal. (3) The second student used 00 cm 3 of dilute hydrochloric acid instead of 50 cm 3. Explain the effect, if any, this mistake would have on the calculated relative atomic mass of the metal. (3) (Total 7 marks) Page 3 of

32 Lead nitrate solution reacts with potassium iodide solution. The reaction produces a solid. Figure shows the reaction occurring. Figure Lead Iodide By Der Kreole (own work) (CC-BY-3.0) via Wikimedia Commons (a) (i) Give the name of this type of reaction. Tick ( ) one box. Combustion Neutralisation Precipitation () Write the missing state symbols in the chemical equation. Pb(NO 3 ) 2 (aq) + 2KI( ) PbI 2 ( ) + 2KNO 3 (aq) (iii) Complete the word equation for the reaction. lead nitrate + lead iodide + Page 32 of

33 (iv) How is solid lead iodide separated from the solution? Draw a ring around the correct answer. Distillation Electrolysis Filtration () (b) A group of students investigated the movement of particles. The students filled a container with water. The students added a crystal of lead nitrate at position X and a crystal of potassium iodide at position Y, as shown in Figure 2. Figure 2 view from above After 3 minutes solid lead iodide started to form at the position shown in Figure 3. Figure 3 view from above (i) Tick ( ) the correct box to complete the sentence. Lead ions and iodide ions move through the water by diffusion. evaporation. neutralisation. () Page 33 of

34 What conclusion can you make about the speed of movement of lead ions compared with iodide ions? Give a reason for your answer. (iii) The students repeated the experiment at a higher temperature. The solid lead iodide formed after a shorter period of time. Explain why, in terms of particles. (Total marks) 2 A company manufactures ethanol (C 2 H 5 OH). The reaction for the process is: C 2 H 4 (g) + H 2 O(g) C 2 H 5 OH(g) ΔH = 45 kj per mole The temperature and pressure can be changed to increase the yield of ethanol at equilibrium. (a) Explain what is meant by equilibrium. (3) Page 34 of

35 (b) (i) How would increasing the temperature change the yield of ethanol at equilibrium? Give a reason for your answer. How would increasing the pressure change the yield of ethanol at equilibrium? Give a reason for your answer. (c) A catalyst is added to increase the rate of the reaction. Explain how adding a catalyst increases the rate of a chemical reaction. (Total 9 marks) Page 35 of

36 3 (a) The figure below represents the reaction of sulfur dioxide with oxygen. Oxygen Sulfur dioxide Sulfur trioxide (i) Complete the word equation for the reaction of sulfur dioxide with oxygen. sulfur dioxide + () Draw a ring around the correct answer to complete the sentence. a compound. Sulfur dioxide (SO 2 ) is an element. a mixture. () (b) The reactants are gases. When the pressure of the gases is increased, the reaction gets faster. Complete the sentence. When the pressure of the gases is increased, the frequency of the collisions. () (c) The particles need energy to react. Complete the sentence. The minimum amount of energy that particles need to react is called the energy. () (d) Give one way of increasing the rate of the reaction other than changing the pressure. () (Total 5 marks) Page 36 of

37 4 Some students investigated reactions to produce magnesium. (a) The students used electrolysis to produce magnesium from magnesium chloride, as shown in the figure below. (i) Magnesium chloride contains magnesium ions and chloride ions. Why does solid magnesium chloride not conduct electricity? () One of the products of the electrolysis of molten magnesium chloride is magnesium. Name the other product. () (iii) Why do magnesium ions (Mg 2+ ) move to the negative electrode? () (iv) At the negative electrode, the magnesium ions (Mg 2+ ) gain electrons to become magnesium atoms. How many electrons does each magnesium ion gain? () Page 37 of

38 (b) The students did the experiment four times and weighed the magnesium produced. The table below shows their results. Experiment Mass of magnesium produced in grams (i) There is an anomalous result. Suggest one possible reason for the anomalous result. () Calculate the mean mass of magnesium produced, taking account of the anomalous result. Mean mass = g Page 38 of

39 (c) The formula of magnesium chloride is MgCl 2 The relative formula mass of magnesium chloride is 95. The relative atomic mass of magnesium is 24. (i) Use the equation to calculate the percentage mass of magnesium in magnesium chloride. Percentage mass of magnesium = 00% Percentage mass of magnesium in magnesium chloride = % Draw a ring around the relative mass of chlorine in MgCl () (d) Magnesium is also produced from the reaction of magnesium oxide with silicon. (i) The equation for the reaction is: 2 MgO(s) + Si(s) SiO 2 (s) + 2 Mg(s) What is the meaning of this symbol? Draw a ring around the correct answer. neutralisation reaction precipitation reaction reversible reaction () The forward reaction is endothermic. Draw a ring around the correct answer to complete the sentence. decreases. In an endothermic reaction the temperature of the surroundings increases. stays the same. () (Total 2 marks) Page 39 of

40 5 Figure represents a reaction in the production of sulfuric acid. Figure Oxygen Sulfur dioxide Sulfur trioxide (a) Complete and balance the equation for the reaction. SO 2 (g) + (g) SO 3 (g) (b) The conditions can affect the rate of the reaction. (i) The pressure of the reacting gases was increased. State the effect of increasing the pressure on the rate of reaction. Explain your answer in terms of particles. (3) Page 40 of

41 A catalyst is used for the reaction. The gases pass through a layer containing pieces of the catalyst. Figure 2 shows the shapes of pieces of catalyst. Figure 2 A B Suggest and explain why shape B is more effective as a catalyst than shape A. (c) The reaction is carried out at a high temperature to provide the reactants with the activation energy. What is meant by the activation energy? () Page 4 of

42 (d) Sulfuric acid reacts with metals to produce salts. (i) A student concluded that potassium would not be a suitable metal to react with sulfuric acid. Explain why. A student reacted zinc metal with sulfuric acid to produce a salt and another product. Complete the equation for this reaction. Zn + H 2 SO 4 + (iii) The student wanted to increase the rate of the reaction between the zinc and sulfuric acid. State one way, other than using a catalyst, that the student could increase the rate of the reaction. () (Total 3 marks) Page 42 of

43 6 Carbon dioxide is produced when copper carbonate is heated. A student investigated heating copper carbonate. The student used the apparatus to measure how long it took for carbon dioxide to be produced. The student also noted what happened during each minute for three minutes. (a) The student used changes to the limewater to measure how long it took for carbon dioxide to be produced. Describe how. Page 43 of

44 (b) The student wrote down her observations. Time interval in minutes Between 0 and Between and 2 Between 2 and 3 Observations A slow release of gas bubbles. The limewater did not change. The solid in the test tube was green. A fast release of gas bubbles. The limewater changed at minute 0 seconds. No release of gas bubbles. The solid in the test tube was black. (i) Suggest the reason for the student s observations between 0 and minute. Explain the student s observations between and 2 minutes. (iii) Explain the student s observations between 2 and 3 minutes. Page 44 of

45 7 Thermosoftening polymers can be used to make plastic bottles and food packaging. (a) Why are thermosoftening polymers not suitable for storing very hot food? () (b) The reaction to produce the polymers uses a catalyst. Why are catalysts used in chemical reactions? () (c) Compounds from food packaging must not get into food. Gas chromatography can be used to separate compounds in food. The output from the gas chromatography column can be linked to an instrument which can identify the compounds. (i) Name the instrument used to identify the compounds. () Give one reason why instrumental methods of analysis are used to identify the compounds. () (d) Poly(ethene) is a thermosoftening polymer. Poly(ethene) can be made with different properties. The properties depend on the conditions used when poly(ethene) is made. Suggest two conditions which could be changed when poly(ethene) is made. (Total 6 marks) Page 45 of

46 8 A student investigated the rate of reaction between sodium thiosulfate and dilute hydrochloric acid. The student placed a conical flask over a cross on a piece of paper. The student mixed the solutions in the flask. The solution slowly went cloudy. The student timed how long it took until the cross could not be seen. The equation for the reaction is: Na 2 S 2 O 3 (aq) + 2 HCl(aq) 2 NaCl(aq) + H2O(l) + SO2(g) + S(s) sodium thiosulfate + hydrochloric acid sodium chloride + water + sulfur dioxide + sulfur (a) Explain why the solution goes cloudy. Page 46 of

47 (b) The student repeated the experiment with different concentrations of sodium thiosulfate. Concentration of sodium thiosulfate in moles per dm 3 Time taken until the cross could not be seen in seconds Trial Trial 2 Trial 3 Mean (i) Calculate the mean time for moles per dm 3 of sodium thiosulfate. Mean = seconds Describe and explain, in terms of particles and collisions, the effect that increasing the concentration of sodium thiosulfate has on the rate of the reaction. (3) (Total 7 marks) 9 The following steps show how to use a type of glue. Step Measure out equal amounts of the liquids from tubes A and B. Page 47 of

48 Step 2 Mix the liquids to make the glue. Put a thin layer of the glue onto each of the surfaces to be joined. Step 3 Put the pieces together and hold them with tape. Step 4 Leave the glue to set. (a) When liquids A and B are mixed a chemical reaction takes place. This reaction is exothermic. What does exothermic mean? Page 48 of

49 (b) The time taken for the glue to set at different temperatures is given in the table below. Temperature in C Time taken for the glue to set 20 3 days 60 6 hours 90 hour (i) Use the correct answer from the box to complete each sentence. decreases increases stays the same When the temperature is increased the time taken for the glue to set When the temperature is increased the rate of the setting reaction Tick ( ) two reasons why an increase in temperature affects the rate of reaction. Reason Tick ( ) It gives the particles more energy It increases the concentration of the particles It increases the surface area of the particles It makes the particles move faster (Total 6 marks) Page 49 of

50 20 Sodium thiosulfate solution reacts with hydrochloric acid. As the reaction takes place the solution slowly turns cloudy. The diagram shows a method of measuring the rate of this reaction. A student used this method to study how changing the concentration of the sodium thiosulfate solution alters the rate of this reaction. The student used different concentrations of sodium thiosulfate solution. All the other variables were kept the same. The results of the experiments are shown on the graph below. (a) (i) Draw a line of best fit on the graph. () Suggest two reasons why all of the points do not lie on the line of best fit. Page 50 of

51 Concentration of sodium thiosulfate solution in mol per dm 3 (b) (i) In a conclusion to the experiment the student stated that: The rate of this reaction is directly proportional to the concentration of the sodium thiosulfate. How does the graph support this conclusion? () Explain, in terms of particles, why the rate of reaction increases when the concentration of sodium thiosulfate is increased. (Total 6 marks) Page 5 of

52 2 A student investigated the reaction between magnesium metal and dilute hydrochloric acid. The student placed 25 cm 3 of dilute hydrochloric acid in a conical flask and set up the apparatus as shown in the diagram. The student: took the bung out of the flask and added a single piece of magnesium ribbon 8 cm long put the bung back in the flask and started a stopwatch recorded the volume of gas collected after minute repeated the experiment using different temperatures of acid. The student plotted his results on a graph. Temperature of acid in C Page 52 of

53 Volume = cm 3 () (a) Write the correct state symbols in the equation. Choose from (s) for solid, (l) for liquid, (g) for gas and (aq) for aqueous. Mg (.) + 2 HCl (.) MgCl 2 (.) + H 2 (.) (b) The diagram shows a gas syringe after minute. (i) What volume of gas has been collected in the gas syringe after minute? Use the graph to determine the temperature of the acid used in this experiment. Temperature = C () (iii) Calculate the average rate of reaction, in cm 3 of hydrogen made per second (cm 3 /s), for this experiment. Rate of reaction = cm 3 /s Page 53 of

54 (c) The student s graph has been reprinted to help you answer this question. Temperature of acid in C One of the results on the graph is anomalous. (i) Draw a circle on the graph around the anomalous point. Suggest what may have happened to cause this anomalous result. Explain your answer. () Page 54 of

55 (d) Explain how the student could improve the accuracy of the volume of gas recorded at each temperature. (3) (e) The student then used the same apparatus to measure the volume of gas produced every 0 seconds at 40 C. The student s results are shown on the graph. Time in seconds Page 55 of

56 The rate at which the gas was produced got faster over the first 60 seconds. The student s teacher gave two possible explanations of why the reaction got faster. Explanation There was a layer of magnesium oxide on the surface of the magnesium. The layer of magnesium oxide prevented the magnesium reacting with the acid. As the magnesium oxide reacted slowly with the acid, the magnesium was exposed to the acid and hydrogen gas was produced. Explanation 2 The reaction is exothermic, and so the temperature of the acid increased during the reaction. (i) Describe further experimental work the student could do to see if Explanation is correct. Describe further experimental work the student could do to see if Explanation 2 is correct. (Total 6 marks) Page 56 of

57 22 A student investigated the reaction between magnesium and hydrochloric acid. The equation for the reaction is: Mg(s) magnesium + 2 HCl(aq) hydrochloric acid MgCl2(aq) magnesium chloride + H2(g) hydrogen (a) Give two observations the student could make during the reaction.. 2. Page 57 of

58 (b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. The student investigated how the rate of this reaction changed when the concentration of hydrochloric acid was changed. Write a plan the student could use. In your plan you should: describe how you would carry out the investigation and make it a fair test describe the measurements you would make. (6) (Total 8 marks) Page 58 of

59 23 Read the information and then answer the questions. Cobalt chloride paper can be used to test for water. The paper contains anhydrous cobalt chloride. The jar containing the papers must be kept closed when not being used. The equation shows the reaction between anhydrous cobalt chloride and water. CoCl H 2 O CoCl 2.6H 2 O anhydrous cobalt chloride hydrated cobalt chloride (blue) (pink) (a) Choose one word from the box to complete the sentence. endothermic exothermic reversible The symbol means that the reaction is () (b) Describe the colour change when water is added to the cobalt chloride paper. () (c) Suggest why the jar containing the unused cobalt chloride papers must be kept closed. () (Total 3 marks) Page 59 of

60 24 (a) The symbol equation for the decomposition of hydrogen peroxide is: 2H 2 O 2 2H 2 O + O 2 Complete the word equation for the decomposition of hydrogen peroxide. Hydrogen peroxide + () (b) A student did an experiment to see how quickly hydrogen peroxide decomposes. The student used the apparatus shown below to measure the volume of oxygen. (i) Draw a straight line of best fit to complete the graph. Draw a circle around the anomalous point on the graph. () () Page 60 of

61 cm 3 () (iii) What is the volume of oxygen given off after 5 seconds? (iv) How did the volume of oxygen change between 0 and 25 seconds? () (c) The student wanted to make the reaction faster. Draw a ring around the correct answer to complete each sentence. higher. (i) To make the reaction faster, the temperature should be lower. the same. () more dilute. To make the reaction faster, the hydrogen peroxide should be more concentrated. the same. () (d) The diagram represents the bonding in oxygen. O=O Draw a ring around the correct answer to complete each sentence. share (i) When two oxygen atoms bond, the atoms transfer electrons. delocalise () Page 6 of

62 ionic The oxygen atoms are joined by metallic bonds. covalent () simple molecules. (iii) Oxygen is made of a giant lattice. macromolecules. () (e) When hydrogen peroxide decomposes water is produced. Which two statements in the table explain why water is a liquid at room temperature? Tick ( ) the two statements. Statement Tick ( ) Water has a boiling point of 00 C. Water is made of ions. Water has a melting point lower than room temperature. Water has a giant covalent structure. (Total 2 marks) Page 62 of

63 25 Hand warmers use chemical reactions. (a) The table shows temperature changes for chemical reactions A, B and C. Reaction Starting temperature in C Final temperature in C Change in temperature in C A B C What is the final temperature for reaction B? Write your answer in the table. () (b) (i) What name is given to reactions that heat the surroundings? () Which reaction, A, B or C, would be best to use in a hand warmer? Reaction Give a reason why you chose this reaction. Page 63 of

64 (c) A student added water to some anhydrous copper sulfate. The equation for the reaction is shown. anhydrous copper sulfate + water hydrated copper sulfate CuSO H 2 O CuSO 4.5H 2 O The student measured the temperature before and after the reaction. (i) The measurements showed that this reaction can be used for a hand warmer. Draw a ring around the correct answer to complete the sentence. When water is added to anhydrous copper sulfate the temperature increases. of the mixture decreases. stays the same. () Anhydrous copper sulfate is white. What colour is seen after water is added to the anhydrous copper sulfate? () (iii) What does the symbol mean? () Page 64 of

65 CO + CO 2 (iv) The student heated a tube containing hydrated copper sulfate. Name the solid substance produced. () (Total 8 marks) 26 This question is about gold (Au). (a) An atom of gold is represented as: Au How many neutrons are in this atom of gold? () (b) Gold ions are used as a catalyst. How does a gold atom (Au) become a gold ion (Au 3+ )? (c) A gold catalyst can be used when carbon monoxide reacts with oxygen to make carbon dioxide. (i) Complete and balance the equation for this reaction. Page 65 of

66 Carbon dioxide has a very low boiling point. Explain why. (3) (d) Gold is used as a catalyst in industrial processes. Gold is rare and increasingly expensive. Suggest three reasons why gold is still used in industrial processes. (3) (Total marks) Page 66 of

67 27 A student investigated the reaction of magnesium with hydrochloric acid. (a) A piece of magnesium was dropped into the hydrochloric acid. Bubbles of gas were produced and the magnesium disappeared. The reaction is exothermic. (i) What measurements would the student make to show that the reaction is exothermic? How would these measurements show that the reaction is exothermic? () Page 67 of

68 The student investigated how changing the concentration of the hydrochloric acid affects this reaction. Each test tube contained a different concentration of hydrochloric acid. The diagrams show the results of this experiment. (b) Suggest one control variable in this investigation. () (c) (i) Which test tube, A, B, C or D, contained the greatest concentration of hydrochloric acid? Test tube () Why did you choose this test tube? () Page 68 of

69 (d) The student predicted that if the temperature of the acid was increased the reaction would take place faster. Tick ( ) two statements in the table which explain why. Statement Tick ( ) The particles move faster The particles collide with less energy The particles collide more often The particles are bigger (Total 8 marks) 28 Stage smoke is used for special effects at pop concerts. By Sam Cockman [CC BY 2.0], via Flickr Ammonium chloride can be used to make stage smoke. Ammonium chloride is a white solid. When heated, ammonium chloride produces white smoke which can be blown onto the stage. The equation shows what happens when ammonium chloride is heated and cooled. NH 4 Cl(s) NH 3 (g) + HCl(g) ammonium chloride (white) ammonia (colourless) hydrogen chloride (colourless) Page 69 of

70 (a) The sentences explain how the smoke is made. Draw a ring around the correct answer in each box to complete each sentence. Use the information and the equation to help you. solids. When heated, ammonium chloride makes two colourless liquids. gases. colourless solid. These are blown into the air where they cool and make a black liquid. white gas. ammonia. which is ammonium chloride. hydrogen chloride. (4) (b) Complete the sentence. The symbol means that the reaction is () (Total 5 marks) Page 70 of

71 29 The picture shows a lump of phosphate rock. Rob Lavinsky, irocks.com CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons Phosphoric acid is made by reacting phosphate rock with sulfuric acid. Only three of the methods shown below will increase the rate of this reaction. Put a tick ( ) next to each of the three methods that will increase the rate of this reaction. Method Tick ( ) Use a more concentrated solution of sulfuric acid Use larger lumps of phosphate rock Cool the mixture of phosphate rock and sulfuric acid Grind the phosphate rock into a powder before adding the acid Increase the temperature of the sulfuric acid Dilute the sulfuric acid solution with water (3) (Total 3 marks) Page 7 of

72 30 The picture shows a lump of phosphate rock. Rob Lavinsky, irocks.com CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons Phosphoric acid is made by adding sulfuric acid to phosphate rock. (a) The rate of reaction between sulfuric acid and phosphate rock can be increased if the mixture is heated to a higher temperature. Explain, in terms of particles, why an increase in temperature increases the rate of reaction. (b) State one other way in which the rate of reaction between sulfuric acid and phosphate rock can be increased. () (Total 3 marks) Page 72 of

73 3 Hydrogen peroxide decomposes slowly to give water and oxygen. The reaction is exothermic. 2H 2 O 2 2H 2 O + O 2 (a) In an exothermic reaction, energy is given out. Draw a ring around the correct answer to complete the sentence. goes down. In an exothermic reaction, the temperature goes up. stays the same. () (b) The energy level diagram for this reaction is shown below. The energy changes, A, B and C, are shown on the diagram. Use the diagram to help you answer these questions. (i) Which energy change, A, B or C, is the activation energy? () Which energy change, A, B or C, shows that this reaction is exothermic? () Page 73 of

74 (iii) Hydrogen peroxide decomposes quickly when a small amount of manganese(iv) oxide is added. Draw a ring around the correct answer to complete each sentence. Hydrogen peroxide decomposes quickly because a catalyst. manganese(iv) oxide is an element. a solid. activation energy. The manganese(iv) oxide has lowered the boiling point. temperature. (c) A student did an experiment to find the amount of energy produced when hydrogen peroxide solution is decomposed using manganese(iv) oxide. The apparatus the student used is shown in the diagram. The student first measured the temperature of the hydrogen peroxide. Then the student added the manganese(iv) oxide, stirred the mixture and recorded the highest temperature. (i) Suggest why the student stirred the mixture before recording the highest temperature. () Page 74 of

75 The biggest error in this experiment is heat loss. Suggest how the student could change the apparatus so that less heat is lost. () (Total 7 marks) 32 Hydrogen peroxide decomposes to give water and oxygen. 2H 2 O 2 2H 2 O + O 2 The reaction is exothermic. (a) Explain, in terms of bond breaking and bond making, why the decomposition of hydrogen peroxide is exothermic. () Page 75 of

76 (b) The energy level diagram for this reaction is shown below. The energy changes, A, B and C, are shown on the diagram. Use the diagram to help you answer these questions. (i) How do you know that this reaction is exothermic? () The decomposition of hydrogen peroxide is slow. What does this suggest about energy change B? () Page 76 of

77 (iii) Hydrogen peroxide decomposes quickly when a small amount of manganese(iv) oxide is added. Explain why. (c) A student did an experiment to find the amount of energy produced when hydrogen peroxide solution is decomposed using manganese(iv) oxide. The apparatus the student used is shown in the diagram. The student first measured the temperature of the hydrogen peroxide. Then the student added the manganese(iv) oxide and recorded the highest temperature. The temperature rise was smaller than expected. Suggest why. (Total 7 marks) Page 77 of

78 33 Hydrogen fluoride is used to make hydrofluoric acid. (a) A company makes hydrogen fluoride by reacting solid calcium fluoride with sulfuric acid. The reaction takes place in a rotating kiln. calcium fluoride + sulfuric acid calcium sulfate + hydrogen fluoride The company want this reaction to take place quickly. (i) Rotating the kiln makes the reaction take place faster. Suggest why. () Draw a ring around the correct word in each box. To make the reaction take place faster: higher less the temperature should be so that the particles have energy lower more powder small the solid calcium fluoride should be to give a surface area lumps big dilute less the sulfuric acid solution should be to give collisions concentrated more between the particles each second. (3) Page 78 of

79 (b) The diagram represents a molecule of hydrogen fluoride. The hydrogen and fluorine atoms are joined by a covalent bond. Use the correct word from the box to complete the sentence. electrons neutrons protons In a covalent bond the atoms share. () (c) Hydrogen fluoride is dissolved in water to make an acidic solution of hydrofluoric acid. Draw a ring around the symbol of the ion that makes the solution acidic. H + OH F () (Total 6 marks) Page 79 of

80 34 A student investigated the effect of temperature on the decomposition of hydrogen peroxide. Hydrogen peroxide decomposes to oxygen and water when a manganese(iv) oxide catalyst is added. The student measured the time taken to collect 5 cm 3 of oxygen gas. The apparatus shown below was used for the investigation. The reaction was started by shaking the flask so that the manganese(iv) oxide and hydrogen peroxide were mixed. The student did the investigation at two different temperatures. All the other variables were kept constant. The student s results are shown in the table. Temperature of the hydrogen peroxide solution in C Volume of oxygen collected in cm 3 Time taken to collect the oxygen in seconds Rate of reaction in cm 3 per second (a) (i) Calculate the rate of reaction at 25 C. Rate of reaction = cm 3 per second The teacher said that the student should repeat the investigation to get more results. Suggest why. () Page 80 of

81 (b) The student concluded that: the rate of reaction increases when the temperature is increased. Explain, in terms of particles, why the rate of reaction increases. (Total 5 marks) 35 The diagram shows how anhydrous copper sulfate can be used to test for water. (a) What colour change will you see when water is added to the CuSO 4? Colour changes from to () (b) Draw a ring around the meaning of the symbol endothermic exothermic reversible () (Total 2 marks) Page 8 of

82 Mark schemes (a) Level 3 (5 6 marks): A coherent method is described with relevant detail, which demonstrates a broad understanding of the relevant scientific techniques and procedures. The steps in the method are logically ordered with the dependent and control variables correctly identified. The method would lead to the production of valid results. Level 2 (3 4 marks): The bulk of a method is described with mostly relevant detail, which demonstrates a reasonable understanding of the relevant scientific techniques and procedures. The method may not be in a completely logical sequence and may be missing some detail. Level ( 2 marks): Simple statements are made which demonstrate some understanding of some of the relevant scientific techniques and procedures. The response may lack a logical structure and would not lead to the production of valid results. 0 marks: No relevant content Indicative content remove bung and add magnesium start stopclock / timer measure volume of gas at fixed time intervals repeat with different concentrations of acid control volume of acid control initial temperature of acid control amount / mass / length / particle size of magnesium 6 (b) 6.5 cm 3 (c) all points plotted correctly allow mark for 4 points plotted correctly 2 best fit straight line drawn (d) when the concentration of acid increased the rate of reaction increased or vice versa answer must use the terms rate of reaction linked to concentration [] 2 (a) small molecules with weak intermolecular forces Page 82 of

83 (b) (c) (so) only a small amount of energy is needed to separate the molecules decreases any reference to bonds being weak or being broken negates the second and third mark unless they are stated to be intermolecular bonds or bonds between molecules because the equilibrium shifts in the endothermic direction increases allow reverse reaction favoured if forward reaction is exothermic because there are more molecules of gas on the left-hand side or converse [7] 3 (a) products below reactants correct energy profile activation energy correctly labelled energy given out correctly labelled (b) 3 (%) (c) the products would be above the reactants Page 83 of

84 (d) catalysts increase rate of reaction mark for each property mark for each explanation so products formed in less time or catalysts lower activation energy explanation must be linked correctly to the property to gain the mark so lowers energy requirements or catalysts not used up in the reaction so only an initial outlay needed or only a small amount of catalyst needed (e) (f) (g) so small initial cost Protein high temperatures extremes of ph lactase acts as the lock, lactose is the key (substrate) lactase has an active site which will only fit lactose molecules max. 4 so lactase will not work with other molecules [6] 4 (a) x axis scale correct y axis scale correct all points plotted correctly ± ½ small square Page 84 of

85 curve correct, omitting the anomalous point (b) relative formula mass of NH 4 NO 3 = 4 + (4 ) (3 6) = 80 mass of ammonium nitrate in dm 3 at 20 C = 90 0 = 900 g number of moles of ammonium nitrate in 900 g = 900 / 80 = mol (c) (d) small beads would dissolve slower than fine powder because the surface area of the bead is less than fine powder increasing the temperature at equilibrium will reduce the amount of ammonia produced because the reaction is exothermic increasing the pressure at equilibrium will increase the amount of ammonia produced because the equilibrium will shift towards the smaller number of molecules in the equation (which is ammonia) [3] 5 (a) (as concentration increases) answers must refer to data from graph to gain full marks relationship identified from the graph eg the same volume of gas is collected in a shorter time or more gas is collected in the same time or reaction reaches completion in a shorter time reference to relevant data to evidence relationship eg 20 ml collected in 0 seconds at 0.5 mol / dm 3 in 6.5 s at.0 mol / dm 3 and in 4 s at 2.0 mol / dm 3 or at 0 seconds volume collected is 20 cm 3 with 0.5 mol / dm 3, 30 cm 3 with.0 mol / dm 3, 50 cm 3 with 2.0 mol / dm 3 or total volume collected reaches maximum of 00ml in 20 seconds at 2.0 mol / dm 3 but takes twice as long at.0 mol / dm 3 and at 0.5 mol / dm 3 Page 85 of

86 (b) (c) reactions occur when particles collide increasing concentration means there are more particles in the same volume so there are more collisions leave for longer if gas continues to be produced student A is right or repeat with more acid () if more gas is produced student B is right () [7] 6 (a) 6. circled on table (5 C, test ) (b).8 do not allow.83 (c) (d) 6 (minutes) correct number extrapolated from curve 4.0 min blue / black / purple 7.0 min yellow / orange / brown (e) The amylase solution had been prepared with water at 95 C Page 86 of

87 (f) Level 3 (5 6 marks): A clear and coherent method is described using logical steps and demonstrating a good understanding of how to improve the validity of the method. The method would lead to the production of valid results that would give rise to a more valid conclusion. Level 2 (3 4 marks): The substantive content of a method is present and demonstrates reasonable understanding of how to improve the validity but may be missing some detail. The plan may not be in a completely logical sequence but leads towards the measurement of rate of the reaction. Level ( 2 marks): Simple relevant statements made, which demonstrate limited understanding of how to improve the experimental method. The response lacks logical structure and would not lead to the production of valid results or a more precise optimum temperature. 0 marks: No relevant content Indicative content conduct at a greater range of temperatures use temperatures both above and below 40 C use smaller temperature intervals to get a more accurate optimum (eg go up in 2 C increments) take samples at smaller time intervals to get a more accurate result for time taken control the volume of starch used (eg 5 cm 3 ) control the volume of the amylase solution (eg cm 3 ) control the temperature (eg using a water bath) heat the two solutions separately before mixing control the concentration of the starch solution control the concentration of the amylase solution 6 [3] 7 (a) sulfur / sulphur / S / S(s) (b) as the temperature increases, the rate of reaction increases allow two correct values for rate quoted (from graph) at different temperatures the rate of increase increases or there is an exponential relationship accept the rate of reaction increases slowly (from 20 C to 50 C) then increases more rapidly for 2 marks answer MUST be based on rate / speed of reaction Page 87 of