yr 11 paper 2 Feb half term

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1 yr paper 2 Feb half term Chemistry Higher Name: Class: Date: Time: 79 minutes Marks: 77 marks Comments: Multiple choice questions: Structured questions: Page

2 Q.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: Na2S2O3(aq) + 2 HCl(aq) 2 NaCl(aq) + S(s) + SO2(g) + H2O(l) Name the product that made the mixture go cloudy. () (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 2

3 ... (2) (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 (2) (ii) 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) Q2.This question is about hydrocarbons. (a) Most of the hydrocarbons in crude oil are alkanes. (i) Large alkane molecules can be cracked to produce more useful molecules. The equation shows the cracking of dodecane. Give two conditions used to crack large alkane molecules. Page 3

4 (2) (ii) The products hexene and ethene are alkenes. Complete the sentence. When alkenes react with bromine water the colour changes from orange to.... () (iii) Butane (C4H0) is an alkane. Complete the displayed structure of butane. () (b) A group of students investigated the energy released by the combustion of four hydrocarbon fuels. The diagram below shows the apparatus used. Each hydrocarbon fuel was burned for two minutes. Table shows the students results. Table After two minutes Name and formula of hydrocarbon fuel Mass of fuel used in g Temperature increase of water in C Energy released by fuel in kj Energy released by.0 g of fuel in kj Relative amount of smoke in the flame Hexane, C6H very little smoke Octane, C8H some smoke Decane, C0H smoky Dodecane, C2H very smoky (i) Calculate the energy released by.0 g of decane in kj. Page 4

5 Energy released =... kj (2) (ii) Suggest one improvement to the apparatus, or the use of the apparatus, that would make the temperature increase of the water for each fuel more accurate. Give a reason why this is an improvement.... (2) (iii) The students noticed that the bottom of the beaker became covered in a black substance when burning these fuels. Name this black substance. Suggest why it is produced.... (2) (iv) A student concluded that hexane is the best of the four fuels. Give two reasons why the results in Table 2 support this conclusion (2) (c) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Most car engines use petrol as a fuel. Petrol is produced from the fractional distillation of crude oil. Crude oil is a mixture of hydrocarbons. Sulfur is an impurity in crude oil. Car engines could be developed to burn hydrogen as a fuel. Page 5

6 Hydrogen is produced from natural gas. Natural gas is mainly methane. Table 2 shows information about petrol and hydrogen. Table 2 State of fuel at room temperature Word equation for combustion of the fuel Petrol Liquid petrol + oxygen carbon dioxide + water Hydrogen Gas hydrogen + oxygen water Energy released from combustion of g of the fuel 47 kj 42 kj Describe the advantages and disadvantages of using hydrogen instead of petrol in car engines. Use the information given and your knowledge and understanding to answer this question.... (6) (Total 8 marks) Q3. Read the article. Page 6

7 Problem food colourings Scientists say they have evidence that some food colourings cause hyperactive behaviour in young children. These food colourings are added to some sweets. W, X, Y and Z are food colourings that may cause hyperactive behaviour in young children. A scientist used chromatography to see if these food colourings were used in two sweets, S &P. The results are shown on the chromatogram. (a) Food colourings, such as W, X, Y and Z, are added to some sweets. Suggest one reason why... () (b) In chromatography, the Rf value = Use the scale on the chromatogram to help you to answer this question. Which food colouring, W, X, Y or Z, has an Rf value of 0.7? (c) From the chromatogram, what conclusions can the scientist make about the colourings in sweets S and P? () Page 7

8 ... (3)(Total 5 marks) 4.Marble chips are mainly calcium carbonate (CaCO3). A student investigated the rate of reaction between marble chips and hydrochloric acid (HCl). Figure shows the apparatus the student used. Figure (a) Complete and balance the equation for the reaction between marble chips and hydrochloric acid CaCl (2) (b) The table below shows the student s results. Time in s Volume of gas in dm On Figure 2: Page 8

9 Plot these results on the grid. Draw a line of best fit. Figure 2 (4) (c) Sketch a line on the grid in Figure 2 to show the results you would expect if the experiment was repeated using 20 g of smaller marble chips. Label this line A. (2) (d) Explain, in terms of particles, how and why the rate of reaction changes during the reaction of calcium carbonate with hydrochloric acid. (4) (e) Another student investigated the rate of reaction by measuring the change in mass. Figure 3 shows the graph plotted from this student s results. Figure 3 Page 9

10 Use Figure 3 to calculate the mean rate of the reaction up to the time the reaction is complete. Give your answer to three significant figures. Mean rate of reaction =... g / s (4) (f) Use Figure 3 to determine the rate of reaction at 50 seconds. Show your working on Figure 3. Give your answer in standard form. Rate of reaction at 50 s =... g / s (4) (Total 20 marks) Q5. Ethanol (C2H5OH) is produced from ethene or from sugar cane. Page 0

11 The two different methods to produce ethanol are summarised in the table. Ethanol from sugar cane is a batch process Sugar cane plants are crushed and soaked in water for one day. The sugar solution is separated by filtration. Ethanol from crude oil is a continuous process Crude oil is distilled to separate the naphtha fraction. The naphtha fraction is cracked when the vaporised hydrocarbons are passed over a hot catalyst. Yeast is added to the sugar solution and The ethene produced is separated by fermented for three days. distillation. The solution of water and ethanol produced is separated by filtration. Distillation of this solution produces a 50% solution of ethanol. Ethene is reacted with steam in the presence of a catalyst. This hydration reaction produces 00% ethanol. (a) Complete and balance an equation for the cracking of the hydrocarbon C6H4 to produce ethene. C6H (2) (b) What is seen when the sugar solution and yeast are fermented?... () (c) Evaluate the issues involved with the production of ethanol from sugar cane compared with the production of ethanol from crude oil. You should explain why each issue you describe is important. Page

12 (5) (Total 8 marks) Q6.A student investigated food dyes using paper chromatography. This is the method used.. Put a spot of food colouring X on the start line. 2. Put spots of four separate dyes, A, B, C and D, on the start line. 3. Place the bottom of the paper in water and leave it for several minutes. Figure shows the apparatus the student used. Figure (a) Write down two mistakes the student made in setting up the experiment and explain what problems one of the mistakes would cause.... (2) (b) Another student set up the apparatus correctly. Figure 2 shows the student s results. The result for dye D is not shown. Figure 2 Page 2

13 Calculate the Rf value of dye A Give your answer to two significant figures. Rf value =... (3) (c) Dye D has an Rf value of Calculate the distance that dye D moved on the chromatography paper. Distance moved by dye D =... () (d) Explain how the different dyes in X are separated by paper chromatography. Page 3

14 .. (4) (e) Flame emission spectroscopy can be used to analyse metal ions in solution. Figure 3 gives the flame emission spectra of five metal ions, and of a mixture of two metal ions. Figure 3 Use the spectra to identify the two metal ions in the mixture.... (2) (f) Explain why a flame test could not be used to identify the two metal ions in the mixture... (2) (g) Two students tested a green compound X. The students added water to compound X. Compound X did not dissolve. Page 4

15 The students then added a solution of ethanoic acid to compound X. A gas was produced which turned limewater milky. Student A concluded that compound X was sodium carbonate. Student B concluded that compound X was copper chloride. Which student, if any, was correct? Explain your reasoning. (4) (Total 8 marks) Page 5

16 Chemistry Higher Half term Mock paper 2 m/s Multiple choice questions:. C 2H 6 mark.2 Alkanes mark.3 Cracking mark Structured Questions M.(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 (c) (i) any two from: temperature (of the reactants) concentration of hydrochloric acid volume of hydrochloric acid volume of sodium thiosulfate the (size / darkness / thickness of the) cross total volume of solution. if no other marks gained, allow mark for: rate of stirring OR amount of hydrochloric acid / sodium thiosulfate OR volume of solution 2 (ii) (because as the concentration increases) the number of particles per unit volume increases or particles are closer together. idea of more particles in a given space is required for the first mark. ignore references to area. (therefore) the frequency of (successful) collisions increases allow increased chance / probability of collisions number of collisions increases is insufficient here. must mention per unit time or frequency. ignore speed of collisions. if reference to space and time missing from M and M2 but Page 6

17 they are otherwise correct, then award mark. so the number of particles (per unit volume) doubles or (the frequency of) collisions doubles. students can score 2 marks for a qualitative explanation; the third mark is for a quantitative explanation. [8] M2.(a) (i) high temperature allow heating / hot / C catalyst or steam allow named catalyst eg zeolite, Al 2O 3, silica, ceramic allow in the absence of air / oxygen ignore any references to pressure (ii) colourless allow decolourised ignore clear / discoloured (iii) (b) (i) 20.3(0) (kj) if answer incorrect allow mark for 24.36/.2 2 (ii) use a lid allow insulate beaker or use draught shield Page 7

18 reduce energy / heat loss ignore references to thermometer or repeats or distance of flame or loss of water vapour allow stir () to distribute energy / heat () allow use a metal can () as it s a better conductor () (iii) carbon/soot ignore tar, smoke (produced by) incomplete combustion allow from a limited supply of oxygen/air (iv) hexane gives out the greatest energy (per.0 g) ignore more energy hexane produces the least smoke / carbon / soot allow has the cleanest flame ignore less smoke / carbon / soot (c) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also apply a best-fit approach to the marking. Level 3 (5 6 marks): Descriptions of advantages and disadvantages that are linked to their own knowledge. Level 2 (3 4 marks): Descriptions of an advantage and a disadvantage with some use of their knowledge to add value. Level ( 2 marks): Statements made from the information that indicate whether at least one statement is an advantage or a disadvantage or a linked advantage or disadvantage 0 marks: No relevant content Examples of the added value statements and links made in the response Page 8

19 could include: Note that link words are in bold; links can be either way round. Accept reverse arguments and ignore cost throughout. Advantages of using hydrogen: Combustion only produces water so causes no pollution Combustion does not produce carbon dioxide so this does not contribute to global warming or climate change Combustion does not produce sulfur dioxide so this does not contribute to acid rain Incomplete combustion of petrol produces carbon monoxide that is toxic Incomplete combustion of petrol produces particulates that contribute to global dimming Petrol comes from a non-renewable resource but there are renewable/other methods of producing hydrogen Hydrogen releases more energy so less fuel needed or more efficient Disadvantages of using hydrogen: Hydrogen is a gas so is difficult to store or transfer to vehicles Hydrogen gas is very flammable so leaks cause a greater risk of explosion Most hydrogen is produced from fossil fuels which are running out Cannot be used in existing car engines so modification / development or replacement is needed Lack of filling stations so difficult to refuel your vehicle 6 [8] M3. (a) (improve) appearance allow add colour allow these food colourings have not been proven to cause hyperactive behaviour in young children do not accept taste / flavour / preservatives ignore reference to E-numbers (b) X (c) any three from: S contains six / 6 colourings P contains five / 5 colourings if neither of first 2 bullet points given allow mark for S contains more colours than P or converse both S and P contain the same five / 5 colourings Page 9

20 both contain W and Y both sweets (may) cause hyperactivity ignore unsafe neither contain X and Z 3 [5] M4.(a) CaCO3 + 2HCl CaCl2 + H2O + CO2 2 allow mark for correct formulae (b) sensible scales, using at least half the grid for the points all points correct ± ½ small square allow mark if 8 or 9 of the points are correct 2 best fit line (c) steeper line to left of original line finishes at same overall volume of gas collected (d) acid particles used up allow marble / reactant used up Page 20

21 so concentration decreases allow surface area of marble decreases so less frequent collisions / fewer collisions per second do not accept fewer collisions unqualified so rate decreases / reaction slows down (e) mass lost of 2.2 (g) time taken of 270 s allow values in range allow ecf for values given for mass and time (g / s) or (f) allow mark for correct calculation of value to 3 sig figs accept or with no working shown for 4 marks correct tangent eg 0.35 / 50 Page 2

22 0.007 allow values in range of accept with no working shown for 4 marks [20] M5. (a) C2H4 a correct other product and balanced eg C4H0 (b) bubbling / fizzing / frothing / effervescence ignore gas given off or solution goes cloudy (c) any five from the following bullet points: allow converse for ethanol from crude oil To gain full marks there should be both advantageous and disadvantageous issues and their importance Advantageous issues using sugar cane: ignore costs unless specified ignore safety ignore simple/low technology process ignore labour intensive as an advantage linked importance sugar cane/plants absorb carbon dioxide / photosynthesise so is carbon neutral or reduce global warming sugar cane / plants are renewable / sustainable and so save resources / oil or crude oil is non-renewable Page 22

23 low energy process and so it saves fuel or / making ethanol from crude oil needs fuel for fractional distillation / cracking Disadvantageous issues using sugar cane: ignore fermentation releases carbon dioxide; destruction of habitats/land to build production plants; types of pollution; waste products large areas of land are needed which leads to destruction of habitats / forest land could be used for food crops may cause food shortages or increases the price of food or increasing world population slow process so limits supply / production of ethanol ethanol is impure or contains 50% ethanol so needs further separation or ethanol from crude oil is 00% pure batch process so uses more labour the crop yield / supply of ethanol is unreliable because growth is seasonal / weather dependent or possibility of crop failure a justified conclusion compensation mark, if no other mark awarded allow one mark for two or more issues 5 [9] M6.(a) water level above the start line and start line drawn in ink allow water level too high water level food colours would dissolve into water Page 23

24 or start line the ink would run on the paper (b) (distance moved by A) 2.8cm and 8.2 cm (distance moved by solvent) allow values in range cm and cm 0.34 allow 0.33 or 0.35 allow ecf from incorrect measurement to final answer for 2 marks if given to 2 significant figures accept 0.34 without working shown for 3 marks (c) 6.6 cm allow values between 6.48 and 6.64 cm (d) solvent moves through paper different dyes have different solubilities in solvent and different attractions for the paper and so are carried different distances (e) calcium ions allow Ca 2+ Page 24

25 sodium ions allow Na + (f) two different colours or Ca 2+ / one is orange-red and Na + / the other is yellow allow brick red for Ca 2+ and / or orange for Na + allow incorrect colours if consistent with answer to 7.5 (so) colours mix or (so) one colour masks the other (g) (Student A was incorrect) because sodium compounds are white not green or because sodium carbonate is soluble so can t contain sodium ions (Student B was incorrect) because adding acid to carbonate produces carbon dioxide so must contain carbonate not chloride ions [8] Page 25