page 13 30. Which of the following diagrams shows the apparatus correctly set up for heating under reflux? water in A water out water in C water out heating mantle heating mantle heating mantle heating mantle water in D water out water in B water out [END OF SECTION 1. NOW ATTEMPT THE QUESTIONS IN SECTION 2 OF YOUR QUESTION AND ANSWER BOOKLET] page 14 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 15 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 16 [BLANK PAGE] DO NOT WRITE ON THIS PAGE AH 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 You may refer to the Chemistry Data Booklet for Higher and Advanced Higher. Total marks — 100 SECTION 1 — 30 marks Attempt ALL questions. Instructions for the completion of Section 1 are given on page 02. SECTION 2 — 70 marks Attempt ALL questions. 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. X713/77/01 MONDAY, 21 MAY 9:00 AM – 11:30 AM A/PB Chemistry Section 1 — Answer Grid and Section 2 page 02 SECTION 1 — 30 marks The questions for Section 1 are contained in the question paper X713/77/02. 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 A B C D 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 SECTION 1 — Answer Grid [Turn over page 04 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 05 MARKS DO NOT WRITE IN THIS MARGIN SECTION 2 — 70 marks Attempt ALL questions 1. Roman pottery contains traces of metals. (a) The metals present in Roman pottery can be identified using atomic emission spectroscopy. Analysis of a sample from a Roman pot produced a series of spectral lines. The data in the table shows the results for three of the spectral lines produced. Metal Wavelength of spectral line (nm) Relative intensity aluminium 620 651 589 485 titanium 498 375 (i) Name the metal that produces the orange-yellow spectral line at 589 nm. (ii) A fourth line observed in the spectrum obtained from the Roman pot sample was caused by a transition with an energy value of 282 kJ mol-1. Calculate the wavelength, in nm, of this spectral line. (iii) The Roman pot sample was found to have a titanium content of 435 mg kg-1. A different pot sample produced a spectral line at 498 nm with a relative intensity of 75. Calculate the titanium content, in mg kg-1, for this sample. 1 2 1 [Turn over page 06 MARKS DO NOT WRITE IN THIS MARGIN 1. (continued) (b) The Romans may have inadvertently made aluminium metal while producing pottery. Aluminium has the following electronic configuration. 1s2 2s2 2p6 3s2 3p1 (i) This electronic configuration is consistent with the aufbau principle. State the aufbau principle. (ii) For the 3p electron in aluminium, complete the table to show one possible set of values for the four quantum numbers. Quantum number n l m s Value 1 1 page 07 MARKS DO NOT WRITE IN THIS MARGIN 2. Apple jam contains malic acid. HO C C CH2 CH OH O O OH malic acid (a) Malic acid dissociates in two stages. The equation for the first stage dissociation of malic acid is HOOCCH2CH(OH)COOH(aq) + H2O(ℓ) Ý HOOCCH2CH(OH)COO−(aq) + H3O+(aq) (i) Write an expression for the first stage dissociation constant, Ka, for malic acid. (ii) Complete the equation to show the second stage dissociation of malic acid. HOOCCH2CH(OH)COO−(aq) + H2O(ℓ) Ý 1 1 [Turn over page 08 MARKS DO NOT WRITE IN THIS MARGIN 2. (continued) (b) While making apple jam, the jam will only thicken if the pH is between 2·7 and 3·3. (i) The pH of the apple jam is determined by the first stage dissociation of malic acid (Ka = 3·2 × 10-4). The concentration of malic acid in the jam is 0·0051 mol l-1. Show by calculation that the jam will thicken at this concentration of malic acid. 3 page 09 MARKS DO NOT WRITE IN THIS MARGIN 2. (b) (continued) (ii) Pectin is a natural polymer found in apples which helps jam to thicken. Part of the structure of pectin is shown. O O CO2H HO OH O O OH HO O O HO CO2CH3 CO2CH3 OH O Pectin binds to itself to help the jam thicken. Suggest how the hydroxyl groups allow pectin molecules to bind. 1 [Turn over page 10 MARKS DO NOT WRITE IN THIS MARGIN 3. Sodium carbonate can exist as different hydrated salts with the general formula Na2CO3.nH2O. To determine n in the general formula, a 250 cm3 solution containing 8·10 g of hydrated sodium carbonate was prepared. 25·0 cm3 samples of this solution were titrated with 0·358 mol l-1 hydrochloric acid. Na2CO3(aq) + 2HCl(aq) ↓ 2NaCl(aq) + H2O(ℓ) + CO2(g) The following results were obtained. Titre Volume of HCl added (cm3) 1 20·2 2 19·5 3 19·4 (a) Describe the procedure for the accurate preparation of the 250 cm3 solution from the weighed sample of hydrated sodium carbonate. 2 page 11 MARKS DO NOT WRITE IN THIS MARGIN 3. (continued) (b) (i) Calculate the number of moles of sodium carbonate in the 250 cm3 solution. (ii) Calculate the value of n in the formula Na2CO3.nH2O 2 2 [Turn over page 12 MARKS DO NOT WRITE IN THIS MARGIN 3. (continued) (c) Titration is a very useful analytical technique for volumetric analysis. Using your knowledge of chemistry, discuss factors which should be considered when selecting appropriate chemicals for a titration. 3 page 13 MARKS DO NOT WRITE IN THIS MARGIN 4. But-2-yne and but-1-yne can undergo addition reactions with hydrogen using a palladium-based catalyst. H3C C C CH3 CH2CH3 H C C but-1-yne but-2-yne (a) State how transition metals can act as catalysts. (b) In the reaction of but-2-yne with hydrogen, cis-but-2-ene is formed. Draw the skeletal structure of cis-but-2-ene. (c) In the reaction of but-1-yne with hydrogen, but-1-ene is formed. Explain why but-1-ene has no geometric isomers. 1 1 1 [Turn over page 14 MARKS DO NOT WRITE IN THIS MARGIN 4. (continued) (d) The equation for the hydrogenation of but-2-yne is shown. C4H6(ℓ) + H2(g) ↓ C4H8(g) Substance Standard free energy of formation, ∆G°f (kJ mol-1) Standard enthalpy of formation, ∆H°f (kJ mol-1) C4H6(ℓ) 185 119 H2(g) 0 0 C4H8(g) 65·9 -6·99 (i) For the hydrogenation of but-2-yne, use the data in the table to calculate: (A) the standard enthalpy change, ∆H°, in kJ mol-1; (B) the standard entropy change, ∆S°. 1 3 page 15 MARKS DO NOT WRITE IN THIS MARGIN 4. (d) (continued) (ii) Calculate the temperature, in K, below which this reaction is feasible. 2 [Turn over page 16 MARKS DO NOT WRITE IN THIS MARGIN 5. Some dyes contain molecules that are coloured. The structures of two different dye molecules are shown below. S S N N + S N + N S blue-green purple (a) State the structural feature present that is responsible for the colour of these dye molecules. (b) Explain fully how colour arises in these dye molecules. 1 2 page 17 MARKS DO NOT WRITE IN THIS MARGIN 5. (continued) (c) A third dye molecule has the following structure. N + N S S Explain fully why this dye molecule will absorb a shorter wavelength of light than the other two dye molecules. 2 [Turn over page 18 MARKS DO NOT WRITE IN THIS MARGIN 6. Ligands can be used in medicine and in quantitative analysis. (a) Explain how ligands bond to metal ions to form complexes. (b) DMPS is a ligand that can be used to treat mercury poisoning. DMPS SH SH S HO O O (i) Write the molecular formula for DMPS. 1 1 page 19 MARKS DO NOT WRITE IN THIS MARGIN 6. (b) (continued) (ii) A possible structure for the mercury-DMPS complex is S Hg S S S S OH S HO O O O O (A) State the term used to classify the DMPS ligand in this complex. (B) State the co-ordination number of mercury in this complex. 1 1 [Turn over page 20 MARKS DO NOT WRITE IN THIS MARGIN 6. (continued) (c) Nisil is an alloy of nickel and silicon. The mass of nickel in the Nisil alloy can be determined by quantitative analysis using a procedure in which the ligand dimethylglyoxime forms a solid complex with nickel ions. This complex is collected, dried and weighed. C C N Ni N N C C N CH3 CH3 H3C H3C O O H O O H nickel-dimethylglyoxime complex GFM 288·7 g (i) Name the type of quantitative analysis being carried out. (ii) It was found that 1∙02 g of Nisil alloy formed 4∙82 g of the complex. Calculate the percentage by mass of nickel in the alloy. 1 2 page 21 [Turn over for next question DO NOT WRITE ON THIS PAGE page 22 MARKS DO NOT WRITE IN THIS MARGIN 7. Adrenaline is a natural hormone produced in the body. HO HO N OH H adrenaline (a) Adrenaline can be artificially synthesised in the process shown below. HO X HO N OH H N O H O HO HO Cl O Cl Cl + O Cl O H HO HO N + CH3NH2 HO HO HO HO HO HO Step 1 Step 2 Step 3 page 23 MARKS DO NOT WRITE IN THIS MARGIN 7. (a) (continued) (i) Suggest the type of chemical reaction taking place in step 1. (ii) The aromatic product formed in step 2 contains an amine functional group. State the type of amine formed. (iii) Name reagent X used in step 3. (iv) Identify the step(s) in which the product has a carbon chiral centre. 1 1 1 1 [Turn over page 24 MARKS DO NOT WRITE IN THIS MARGIN 7. (continued) (b) Adrenaline is used as a treatment for severe allergic reactions. A typical dose contains 0·3 cm3 of 500 ppm adrenaline solution. Calculate the mass of adrenaline, in mg, delivered in one dose. (c) Adrenaline can be extracted from the leaves of the agnimantha plant. The adrenaline extracted can be identified using thin layer chromatography, TLC. Complete and label the diagram to show how the TLC should be set up to compare the extracted adrenaline with a sample of pure adrenaline. (An additional diagram, if required, can be found on page 36). solvent TLC plate chromatography tank 1 1 page 25 [Turn over for next question DO NOT WRITE ON THIS PAGE page 26 MARKS DO NOT WRITE IN THIS MARGIN 8. Ethanol biofuel can be made from corn starch. The flow diagram shows the steps involved in the production of ethanol biofuel. pure ethanol biofuel 96% ethanol solution 13% ethanol solution Step 3 Pass through a molecular sieve Step 2 Distillation Step 1 Hydrolysis and fermentation corn starch in water (a) Step 1 produces a solution with a concentration of 13% ethanol by volume. This can be checked by measuring the density of the solution and comparing it to a calculated value. The density of the solution can be calculated using the following expression. 1 2 100 m m d + = d = density of solution, in g cm-3 m1 = mass of ethanol, in g, in 100 cm3 of solution m2 = mass of water, in g, in 100 cm3 of solution Mass of 1 cm3 of ethanol = 0·79 g Mass of 1 cm3 of water = 1·00 g Calculate the density of the ethanol solution, in g cm-3, formed in step 1. 2 page 27 MARKS DO NOT WRITE IN THIS MARGIN 8. (continued) (b) In step 2, 96% ethanol solution is produced by distillation. Suggest why pure ethanol biofuel cannot be obtained from an ethanol/water mixture by distillation alone. (c) Step 3 uses a molecular sieve to remove water from the 96% ethanol solution. Part of the structure of a molecular sieve is shown. 0·3 nm Suggest how this molecular sieve could remove the water. 1 1 [Turn over page 28 MARKS DO NOT WRITE IN THIS MARGIN 8. (continued) (d) Ethanol can also be prepared by a nucleophilic substitution reaction. Using your knowledge of chemistry, discuss the role of nucleophilic substitution reactions in the preparation of other chemicals. 3 page 29 [Turn over for next question DO NOT WRITE ON THIS PAGE page 30 MARKS DO NOT WRITE IN THIS MARGIN 9. A mixture of butan-1-ol and butan-2-ol can be synthesised from 1-bromobutane in a two-stage process. H C H H C H H C H H C Br H H H H H C H H C H H C C H H ethanolic KOH stage 1 H C H H C H H C C H H H2O/H+ stage 2 H C H H C H H C H H C OH H H H C H H C H H C OH H C H H H + (a) Name the type of chemical reaction taking place in stage 1. (b) Using structural formulae and curly arrow notation, outline a possible mechanism for the production of butan-2-ol in stage 2. 1 3 page 31 MARKS DO NOT WRITE IN THIS MARGIN 9. (continued) (c) The high-resolution proton NMR spectrum for butan-2-ol is shown. 0 1 2 3 5 4 ppm Circle the hydrogen atom(s) on the structure below responsible for the multiplet at 3∙7 ppm. (An additional structure, if required, can be found on page 36). H C H H C H H C H OH C H H H 1 [Turn over page 32 MARKS DO NOT WRITE IN THIS MARGIN 9. (continued) (d) Butan-1-ol can also be synthesised from 1-bromobutane by a different type of chemical reaction. An experiment was carried out to determine the kinetics for the reaction. Under certain conditions, the following results were obtained. [C4H9Br] (mol l-1) [OH-] (mol l-1) Initial rate (mol l-1 s-1) 0∙25 0∙10 3∙3 × 10-6 0∙50 0∙10 6∙6 × 10-6 (i) The reaction is first order with respect to both reactants. Write the overall rate equation for the reaction. (ii) Calculate the value for the rate constant, k, including the appropriate units. 1 2 page 33 MARKS DO NOT WRITE IN THIS MARGIN 10. Decamethylcobaltocene is a powerful reducing agent. H3C H3C CH3 CH3 CH3 CH3 CH3 CH3 H3C Co2+ H3C decamethylcobaltocene (a) The ligand in decamethylcobaltocene has an aromatic ring. State the feature that provides stability to aromatic rings. (b) Write the electronic configuration, in terms of s, p and d orbitals, for Co2+ in this complex ion. 1 1 [Turn over page 34 MARKS DO NOT WRITE IN THIS MARGIN 10. (continued) (c) Decamethylcobaltocene can be dissolved in petroleum ether to produce a coloured solution. The concentration of this solution can be determined using colorimetry. (i) (A) The first stage is to prepare a calibration graph. Describe fully the procedure required to obtain results that would allow a calibration graph to be drawn. (B) The second stage is to determine the concentration of a sample of the decamethylcobaltocene solution. Describe how this would be carried out. (ii) Name the compound produced when decamethylcobaltocene solution reduces propanal. 2 1 1 page 35 MARKS DO NOT WRITE IN THIS MARGIN 10. (continued) (d) Decamethylcobaltocene oxidises easily creating impurities in the sample. The purity of decamethylcobaltocene can be checked using low-resolution 1H NMR. H3C H3C CH3 CH3 CH3 CH3 CH3 CH3 H3C Co2+ H3C decamethylcobaltocene Predict the number of peaks that would be observed in a low-resolution 1H NMR spectrum of a pure sample of decamethylcobaltocene. [END OF QUESTION PAPER] 1 page 36 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL DIAGRAM FOR USE IN QUESTION 7 (c) solvent TLC plate chromatography tank ADDITIONAL STRUCTURE FOR USE IN QUESTION 9 (c) H C H H C H H C H OH C H H H page 37 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK page 38 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK page 39 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 40 [BLANK PAGE] DO NOT WRITE ON THIS PAGE