page 07 17. Consider the reaction pathways shown below. CO(g) + ½O2(g) X CO2(g) −283 kJ mol−1 −394 kJ mol−1 C(s) + O2(g) According to Hess’s Law, the enthalpy change, in kJ mol−1, for reaction X is A +111 B −111 C −677 D +677. 18. SO3 2−(aq) + H2O(ℓ) ↓ SO4 2−(aq) + 2H+(aq) + 2e− Which of the following ions could be used to oxidise sulfite ions to sulfate ions? A Cr3+(aq) B Al3+(aq) C Fe3+(aq) D Sn4+(aq) 19. During a redox reaction nitrate ions, NO3 −, are converted to nitrogen monoxide, NO. NO3 − ↓ NO Which line in the table correctly completes the ion-electron equation? Reactants Products A 6H+ + 5e− 3H2O B 4H+ + 3e− 2H2O C 6H+ 3H2O + 5e− D 4H+ 2H2O + 3e− [Turn over page 08 20. ICl(ℓ)  +  Cl2(g)    Ý    ICl3(s)    ΔH  =  −106kJ mol−1 Which line in the table identifies correctly the changes that will cause the greatest increase in the proportion of solid in the above equilibrium mixture? Temperature Pressure A decrease decrease B decrease increase C increase decrease D increase increase [END OF SECTION 1. NOW ATTEMPT THE QUESTIONS IN SECTION 2 OF YOUR QUESTION AND ANSWER BOOKLET.] H FOR OFFICIAL USE Fill in these boxes and read what is printed below. Number of seat Town © Mark Full name of centre Forename(s) Surname Scottish candidate number Date of birth Year Day Month National Qualications 2018 Total marks — 100 SECTION 1 — 20 marks Attempt ALL questions. Instructions for the completion of Section 1 are given on page 02. SECTION 2 — 80 marks Attempt ALL questions. You may refer to the Chemistry Data Booklet for Higher and Advanced Higher. Write your answers clearly in the spaces provided in this booklet. Additional space for answers and rough work is provided at the end of this booklet. If you use this space you must clearly identify the question number you are attempting. Any rough work must be written in this booklet. You should score through your rough work when you have written your final copy. Use blue or black ink. Before leaving the examination room you must give this booklet to the Invigilator; if you do not, you may lose all the marks for this paper. X713/76/01 MONDAY, 21 MAY 9:00 AM – 11:30 AM B/HTP Chemistry Section 1 — Answer Grid and Section 2 page 02 SECTION 1 — 20 marks The questions for Section 1 are contained in the question paper X713/76/02. Read these and record your answers on the answer grid on page 03 opposite. Use blue or black ink. Do NOT use gel pens or pencil. 1. The answer to each question is either A, B, C or D. Decide what your answer is, then fill in the appropriate bubble (see sample question below). 2. There is only one correct answer to each question. 3. Any rough working should be done on the additional space for answers and rough work at the end of this booklet. Sample question To show that the ink in a ball-pen consists of a mixture of dyes, the method of separation would be: A fractional distillation B chromatography C fractional crystallisation D filtration. The correct answer is B — chromatography. The answer B bubble has been clearly filled in (see below). A B C D Changing an answer If you decide to change your answer, cancel your first answer by putting a cross through it (see below) and fill in the answer you want. The answer below has been changed to D. A B C D If you then decide to change back to an answer you have already scored out, put a tick (3) to the right of the answer you want, as shown below: A B C D or A B C D page 03 A B C D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 SECTION 1 — Answer Grid [Turn over page 04 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 05 [Turn over for next question DO NOT WRITE ON THIS PAGE page 06 MARKS DO NOT WRITE IN THIS MARGIN SECTION 2 — 80 marks Attempt ALL questions 1. The elements of group 7 in the periodic table are known as the halogens. (a) Going down group 7 the electronegativity of the halogens decreases. (i) State what is meant by the term electronegativity. (ii) Explain why electronegativity values decrease going down group 7. (b) Explain fully why the boiling points of the halogens increase going down group 7. In your answer you should name the intermolecular forces involved. 1 1 3 page 07 MARKS DO NOT WRITE IN THIS MARGIN 2. The elements sodium to argon form the third period of the periodic table. (a) Explain the decrease in atom size going across the third period from sodium to argon. (b) Elements in the third period of the periodic table form chlorides. The structures of three of these chlorides are shown. Cl Si Cl Cl Cl P Cl S Cl Cl Cl Cl (i) Circle the structure of the molecule above that contains bonds with the lowest polarity. (An additional diagram, if required, can be found on page 37). (ii) Explain fully why, of these three chlorides, silicon tetrachloride is the most soluble in hexane. [Turn over 1 1 2 page 08 MARKS DO NOT WRITE IN THIS MARGIN 2. (continued) (c) Silicon tetrachloride can be used to make silicon nitride (Si3N4), a compound found in many cutting tools. (i) Silicon nitride has a melting point of 1900 °C and does not conduct electricity when molten. Explain fully, in terms of structure and bonding, why silicon nitride has a high melting point. (ii) An equation for the formation of silicon nitride is shown. 3SiCl4    +    16NH3    ↓    Si3N4    +    12NH4Cl mass of mass of mass of mass of one mole one mole one mole one mole = 170·1 g = 17·0 g = 140·3 g = 53·5 g Calculate the atom economy for the formation of silicon nitride. 2 2 page 09 MARKS DO NOT WRITE IN THIS MARGIN 2. (continued) (d) Aluminium, another element in the third period, also forms a chloride. Aluminium chloride is prepared by reacting aluminium metal and chlorine gas. Chlorine gas is produced by the reaction between hydrochloric acid and sodium hypochlorite. The chlorine is then passed over heated aluminium foil, forming aluminium chloride as a hot gas. The hot aluminium chloride gas and unreacted chlorine gas are passed into a flask where the aluminium chloride cools to a fine white powder. For safety it is important that any unreacted chlorine gas can escape from the flask. (i) Complete a labelled diagram to show an apparatus suitable for carrying out this preparation. (An additional diagram, if required, can be found on page 37). hydrochloric acid sodium hypochlorite solution (ii) Explain why the aluminium foil needs to be heated at the start of the preparation, despite the reaction being highly exothermic. [Turn over 2 1 page 10 MARKS DO NOT WRITE IN THIS MARGIN 3. Methyl benzoate is commonly added to perfumes as it has a pleasant smell. A student carries out a reaction to produce methyl benzoate using the following apparatus. wooden clip supporting small test tube methanol, benzoic acid and catalyst small test tube containing cold water (a) The reaction mixture needs to be heated. Describe a safe method of heating a flammable mixture. (b) Suggest a reason why there is a small test tube filled with cold water in the neck of the tube containing the reaction mixture. 1 1 page 11 MARKS DO NOT WRITE IN THIS MARGIN 3. (continued) (c) The chemical reaction involved in the experiment is shown. C6H5COOH(s) + CH3OH(ℓ) ↓ C6H5COOCH3(ℓ) + X benzoic acid methyl benzoate mass of one mass of one mass of one mole = 122 g mole = 32 g mole = 136 g (i) Name product X. (ii) In a laboratory experiment, a student used 5·0 g of benzoic acid and 2·5 g of methanol to produce methyl benzoate. Explain why benzoic acid is the limiting reactant. You must include calculations in your answer. (iii) The student produced 3·1 g of methyl benzoate from 5·0 g of benzoic acid. Benzoic acid costs £39·80 for 500 g. Calculate the cost, in £, of the benzoic acid needed to make 100 g of methyl benzoate using the student’s method. 1 2 2 [Turn over page 12 MARKS DO NOT WRITE IN THIS MARGIN 4. 3-Methylbutanal is a compound that is found in low concentrations in many types of food. The structure of 3-methylbutanal is shown. H C H H C H C H H C O H C H H H (a) Draw a structural formula for a ketone that is an isomer of 3-methylbutanal. (b) Name a reagent which could be used to distinguish between 3-methylbutanal and a ketone. (c) Name the strongest intermolecular force that occurs between 3-methylbutanal molecules. 1 1 1 page 13 MARKS DO NOT WRITE IN THIS MARGIN 4. (continued) (d) 3-Methylbutanal is found in olive oil. Explain fully what can happen to 3-methylbutanal that will cause the olive oil to develop an unpleasant taste. (e) 3-Methylbutanal can be used as a reactant in the production of other compounds. One reaction scheme involving 3-methylbutanal is shown. H C H H C H C H H C O H C H H H H3C C O CH3 H C H H C H C H H C H2O C H H H H C C H O C H H H + H C H H C H C H H C C H H H H C C H O C H H H H H + Step 1 product A propanone 3-methylbutanal Step 2 (i) Explain why step 1 is described as a condensation reaction. (ii) Give the systematic name for product A. 2 1 1 [Turn over page 14 MARKS DO NOT WRITE IN THIS MARGIN 5. Many chemical compounds are related to each other by their structural features, the way they are made and how they are used. Using your knowledge of chemistry, describe the relationships between fats, oils, detergents, soaps and emulsifiers. 3 page 15 [Turn over for next question DO NOT WRITE ON THIS PAGE page 16 MARKS DO NOT WRITE IN THIS MARGIN 6. Skin creams contain many different chemicals. (a) Retinol (vitamin A) promotes cell regeneration. One method of supplying retinol to the skin is by using a skin cream containing the compound retinyl palmitate. C15H31 C O O C20H29 retinyl palmitate Retinyl palmitate is absorbed into the skin and then broken down to form retinol. (i) Name the type of reaction that occurs when retinyl palmitate is broken down to form retinol. (ii) Write a molecular formula for retinol. (b) Skin creams often contain vitamin E to prevent damage to the skin caused by free radicals. (i) Describe how free radicals are formed. 1 1 1 page 17 MARKS DO NOT WRITE IN THIS MARGIN 6. (b) (continued) (ii) Hydroxyl free radicals (•OH) can attack fatty acids present in cell membranes. One step in the chain reaction is shown below. C18H31O2    +    •OH    ↓    C18H30O2•    +    H2O State the name given to this step in the chain reaction. (iii) The antioxidant vitamin E is a free radical scavenger. State how free radical scavengers prevent further chain reactions. [Turn over 1 1 page 18 MARKS DO NOT WRITE IN THIS MARGIN 6. (continued) (c) Palmitoyl pentapeptide-4 is also used in skin creams. CH3(CH2)14 C N C C N C C N C C N C C N O H (CH2)4 NH2 H O H CHOH O H CHOH O H (CH2)4 O H H H CH3 CH3 NH2 H C CH2 OH H C OH O (i) Circle a peptide link in the above structure. (An additional diagram, if required, can be found on page 37). (ii) Palmitoyl pentapeptide-4 is formed from palmitic acid and three different amino acids. Molecule Number of molecules used to form one molecule of palmitoyl pentapeptide-4 palmitic acid 1 threonine 2 serine 1 lysine 2 Draw a structural formula for the amino acid serine. 1 1 page 19 MARKS DO NOT WRITE IN THIS MARGIN 7. Terpenes consist of joined isoprene units (2-methylbuta-1,3-diene). They are classified by the number of isoprene units in the molecule. Class of terpene Number of isoprene units hemiterpene 1 monoterpene 2 sesquiterpene 3 diterpene 4 triterpene 6 (a) Myrcene and humulene are terpenes present in hops which give beer its characteristic flavour and aroma. (i) Circle an isoprene unit on the myrcene structure below. CH2 C H2C CH H2C CH2 CH C H3C CH3 (An additional diagram, if required, can be found on page 38). (ii) Humulene has the molecular formula C15H24. Name the class of terpene to which humulene belongs. [Turn over 1 1 page 20 MARKS DO NOT WRITE IN THIS MARGIN 7. (continued) (b) (i) Squalene, a triterpene, is included in some flu vaccines to enhance the body’s immune response. A single dose of flu vaccine contains 10∙69 mg of squalene. Calculate the mass of squalene required to produce a batch of 500 000 doses of flu vaccine. Your answer must be given in kg. (ii) Squalane is a fully saturated hydrocarbon used in skin moisturising cream. Squalane can be made by the reaction of squalene with hydrogen. H C 3 C CH3 CH CH2 CH2 CH2 C CH CH3 C CH3 CH2 CH2 CH2 CH CH 2 CH2 CH2 CH C CH3 CH C CH3 CH2 CH C CH3 CH3 squalene State the number of moles of hydrogen needed to fully saturate one mole of squalene to produce one mole of squalane. 2 1 page 21 MARKS DO NOT WRITE IN THIS MARGIN 7. (continued) (c) The monoterpene limonene, found in lemon oil, can be converted into the alcohol, terpineol. HC CH2 CH3 CH3 H2C H3C CH2 CH3 C H3C C C C CH HC CH2 H2C CH2 CH OH CH2 limonene terpineol (i) Name the type of reaction taking place. (ii) When terpineol is heated with copper(II) oxide, no reaction takes place. Explain why no reaction takes place. [Turn over 1 1 page 22 MARKS DO NOT WRITE IN THIS MARGIN 8. The alkynes are a homologous family of hydrocarbons. (a) The simplest member of the family is ethyne, C2H2, used in welding torches. H C C H Ethyne can be produced from ethane. H H H H H C C H H C H H C H H H + Using bond enthalpies and mean bond enthalpies from the data book, calculate the enthalpy change, in kJ mol−1, for this reaction. (b) Hess’s Law can be used to calculate the enthalpy change for reactions that do not normally take place, such as the formation of propyne from its elements. 3C(s)    +    2H2(g)    ↓    C3H4(g) Calculate the enthalpy change, in kJ mol−1, for this reaction using the following information. C(s)  +  O2(g) ↓ CO2(g) ΔH = −394 kJ mol−1 H2(g)  +  ½O2(g) ↓ H2O(ℓ) ΔH = −286 kJ mol−1 C3H4(g)  +  4O2(g) ↓ 3CO2(g)  +  2H2O(ℓ) ΔH = −1939 kJ mol−1 2 2 page 23 MARKS DO NOT WRITE IN THIS MARGIN 8. (continued) (c) Propyne, C3H4 (1 mole = 40 g), has been suggested as a possible rocket fuel. (i) The enthalpy of combustion of propyne is −1939 kJ mol−1. Calculate the energy released, in kJ, when 1 kg of propyne is burned completely. (ii) The mass of air required to burn 1 g of fuel can be calculated using the relationship shown. Mass of air, in g  =  4·3 × mass of oxygen, in g, for complete combustion of 1 g of fuel Calculate the mass of air, in g, required to burn 1 g of propyne. C3H4(g)    +    4O2(g)    ↓    3CO2(g)    +    2H2O(ℓ) 1 2 [Turn over page 24 MARKS DO NOT WRITE IN THIS MARGIN 8. (c) (continued) (iii) The table shows the mass of air required to burn 1 g of different fuels. Fuel Mass of 1 mole (g) Mass of air required to burn 1 g ethane 30 16·1 propane 44 15·6 methanol 32 6·5 ethanol 46 9·0 Suggest why methanol and ethanol, compared to the other fuels, require less air to burn 1 g. 1 page 25 [Turn over for next question DO NOT WRITE ON THIS PAGE page 26 MARKS DO NOT WRITE IN THIS MARGIN 9. Ethane-1,2-diol can be made from ethene. (a) The flow chart of an industrial process to produce ethane-1,2-diol is shown. recycling gases liquid by-products oxygen Reactor 2 50–70 °C catalyst Separator 2 Separator 1 Reactor 1 200–300 °C catalyst water oxirane liquid ethane-1,2-diol ethene (i) Industrial processes are designed to maximise profit. Using the flowchart, suggest two ways to maximise profit in this industrial process. 2 page 27 MARKS DO NOT WRITE IN THIS MARGIN 9. (a) (continued) (ii) Name the process used in Separator 2 to separate ethane-1,2-diol from the larger liquid by-products. (b) Explain fully why ethane-1,2-diol is more viscous than propan-1-ol. (c) Draw a structural formula for a diol that contains three carbon atoms. [Turn over 1 2 1 page 28 MARKS DO NOT WRITE IN THIS MARGIN 9. (continued) (d) Ethane-1,2-diol has been found to be harmful to animals. Treatment for affected animals involves using a 20% ethanol solution. (i) The 20% ethanol solution is prepared by accurately measuring 20 cm3 of ethanol and then making up to exactly 100 cm3 with water. Describe the procedure which should be used to prepare 100 cm3 of the 20% ethanol solution. (ii) An affected animal must be treated with 9 doses of 20% ethanol solution. Each dose contains 5 cm3 of the ethanol solution for every kilogram body mass of the animal. Calculate the total volume, in cm3, of the 20% ethanol solution needed to treat a 3·5 kg animal. 2 1 page 29 MARKS DO NOT WRITE IN THIS MARGIN 9. (d) (continued) (iii) Ethane-1,2-diol is harmful because it is oxidised in the body to form glycolic acid. C H H C O OH HO glycolic acid (A) Draw a structural formula for another possible product of oxidation of ethane-1,2-diol. (B) Glycolic acid can be neutralised by sodium hydroxide to form sodium glycolate. Give a formula for sodium glycolate. [Turn over 1 1 page 30 MARKS DO NOT WRITE IN THIS MARGIN 10. The molar volume (in units of litres per mole) is the same for all gases at the same temperature and pressure. Using your knowledge of chemistry, suggest how the molar volume of gases could be measured and compared. Any suitable chemicals and apparatus can be used. Some suggested chemicals and apparatus are given below. Chemicals Apparatus hydrochloric acid gas syringe zinc measuring cylinder magnesium delivery tube calcium stoppers water 500 cm3 flask sodium carbonate vacuum pump calcium carbonate balance cylinder of nitrogen cork ring cylinder of hydrogen burette cylinder of carbon dioxide filter funnel 3 page 31 MARKS DO NOT WRITE IN THIS MARGIN 10. (continued) [Turn over page 32 MARKS DO NOT WRITE IN THIS MARGIN 11. Iodine is required for a healthy diet. Food grown in certain parts of the world is low in iodine. To prevent iodine deficiency in people’s diets, table salt can be ‘iodised’ by the addition of very small quantities of potassium iodide, KI. The number of moles of iodide in a sample of salt can be determined by the following procedure. Step 1 Prepare a standard salt solution by dissolving an accurately weighed sample of iodised salt (50·0 g) in water to give a final volume of 250 cm3. Step 2 Transfer 50 cm3 of salt solution to a conical flask and add excess bromine solution to convert the iodide ions to iodine. Step 3 Titrate the iodine (I2) released with sodium thiosulfate solution (Na2S2O3). (a) Describe a procedure to accurately weigh out a 50·0 g sample of iodised table salt. (b) The overall equation for the reaction of bromine solution with iodide ions is shown. 2I−(aq)  +  Br2(aq)    ↓    I2(aq)  +  2Br−(aq) Write the ion-electron equation for the oxidation reaction. 1 1 page 33 MARKS DO NOT WRITE IN THIS MARGIN 11. (continued) (c) Three samples were prepared as described in step 2. Each sample was titrated with 0∙0010 mol l−1 sodium thiosulfate solution. The results are shown below. Sample Volume of sodium thiosulfate (cm3) 1 10∙0 2 9∙4 3 9∙6 (i) Calculate the average volume, in cm3, of sodium thiosulfate solution that should be used to determine the number of moles of iodine released. (ii) Calculate the number of moles of iodine released from 50 cm3 of the standard salt solution. I2(aq)  +  2Na2S2O3(aq)    ↓    2NaI(aq)  +  Na2S4O6(aq) [Turn over 1 2 page 34 DO NOT WRITE IN THIS MARGIN 12. Many modern antiseptics are based on phenol. The table shows the germ-killing power of some phenol compounds. (a) Compound Structure Germ-killing power (relative to phenol) phenol OH 1·0 4-methylphenol OH CH3 2·5 2-chlorophenol OH Cl 3·6 4-ethylphenol OH C2H5 7·5 2,4-dichlorophenol OH Cl Cl 13·0 4-propylphenol OH C3H7 20·0 2,4,6-trichlorophenol OH Cl Cl Cl 23·0 page 35 MARKS DO NOT WRITE IN THIS MARGIN 12. (a) (continued) (i) Suggest two ways in which structural features increase germ-killing power of phenol compounds. (ii) The names of the phenol compounds in the table are derived from their structures using the following rules. Phenol is used as the parent name for the compound. 1. The –OH functional group is assigned as being on carbon 1 of the ring. 2. The ring can be numbered clockwise or anticlockwise to assign numbers to the other atoms or groups. The numbers should be assigned so that the lowest possible numbers are used. 3. If two or more identical atoms or groups are present, use one of the prefixes di, tri or tetra. 4. The names of the atoms or groups attached to the ring are listed alphabetically (ignoring the prefixes for alphabetical purposes). Using these rules, name this molecule. OH Cl CH3 CH3 [Turn over 2 1 page 36 MARKS DO NOT WRITE IN THIS MARGIN 12. (continued) (b) There are different methods of producing phenol. (i) In the early 1900s, phenol was produced by the following reaction. C6H6  +  H2SO4  +  2NaOH  ↓  C6H5OH  +  Na2SO3  +  2H2O benzene phenol mass of mass of one mole one mole = 78·0 g = 94·0 g Calculate the mass of phenol, in kg, produced from 117 kg of benzene if the percentage yield is 90%. (ii) Phenol is now usually produced by the Cumene Process. C O X O H H+ + CH3 CH3 OH phenol cumene hydroperoxide Name the other product, X, formed in the Cumene Process. [END OF QUESTION PAPER] 2 1 page 37 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK ADDITIONAL DIAGRAM FOR USE IN QUESTION 2 (b) Cl Si Cl Cl Cl P Cl S Cl Cl Cl Cl ADDITIONAL DIAGRAM FOR USE IN QUESTION 2 (d) (i) hydrochloric acid sodium hypochlorite solution ADDITIONAL DIAGRAM FOR USE IN QUESTION 6 (c) (i) CH3(CH2)14 C N C C N C C N C C N C C N O H (CH2)4 NH2 H O H CHOH O H CHOH O H (CH2)4 O H H H CH3 CH3 NH2 H C CH2 OH H C OH O page 38 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK ADDITIONAL DIAGRAM FOR USE IN QUESTION 7 (a) (i) CH2 C H2C CH H2C CH2 CH C H3C CH3 page 39 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK page 40 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK