Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2008 Chemistry Assessment Unit A2 1 assessing Module 4: Further Organic, Physical and Inorganic Chemistry [A2C11] A2C11 THURSDAY 22 MAY, MORNING TIME 1 hour 30 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all fifteen questions. Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering. Answer all five questions in Section B. Write your answers in the spaces provided in this question paper. INFORMATION FOR CANDIDATES The total mark for this paper is 90. Quality of written communication will be assessed in question 14(a)(iv). In Section A all questions carry equal marks, i.e. two marks for each question. In Section B the figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. A2C1S8 3606 For Examiner s use only Question Number Section A 1 10 Section B 11 12 13 14 15 Total
Section A For each of the questions only one of the lettered responses (A D) is correct. Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet. 1 The slowest stage in the production of sulphuric acid involves the conversion of sulphur dioxide to sulphur trioxide. 2SO 2 (g) + O 2 (g) 2SO 3 (g) ΔH = 197 kj What effect does adding a catalyst have on the rates of the forward and reverse reactions and the equilibrium constant? rate of forward reaction rate of reverse reaction equilibrium constant A decreases decreases increases B increases increases increases C increases decreases no effect D increases increases no effect 2 The partition coefficient of an organic compound X between ether and water is 20. An aqueous solution containing 5.00 g of X in 250 cm 3 of water was shaken with 100 cm 3 of ether. What mass of X remained in the aqueous layer following the extraction? A B C D 0.56 g 1.67 g 3.33 g 4.44 g 3 For the reaction H 2 SO 4 + HNO 3 HSO 4 + H 2 NO 3 + HNO 3 is the A conjugate acid of H 2 NO 3 + B conjugate acid of HSO 4 C conjugate base of H 2 NO 3 + D conjugate base of HSO 4 A2C1S8 3606 2 [Turn over
4 Which one of the following reactions in the Born Haber cycle for potassium iodide is exothermic? A KI(s) K + (g) + I (g) B K(g) K + (g) + e C I 2 (g) 2I(g) D I(g) + e I (g) 5 The pharmaceutical drug antifebrin, CH 3 CONHC 6 H 5, is made by the reaction of ethanoic anhydride with phenylamine. (CH 3 CO) 2 O + C 6 H 5 NH 2 CH 3 CONHC 6 H 5 + CH 3 COOH 6.0 g of ethanoic anhydride, (CH 3 CO) 2 O, reacted with 4.0 g of phenylamine, C 6 H 5 NH 2, to produce 3.8 g of antifebrin. The percentage yield is A 48.6% B 63.3% C 65.4% D 95.0% 6 In which one of the following reactions is no gas evolved? A B C D copper metal with concentrated nitric acid concentrated sulphuric acid with solid potassium iodide thionyl chloride with ethanoic acid aqueous sodium sulphite with potassium manganate(vii) solution A2C1S8 3606 3 [Turn over
7 The mechanism for the reaction between propanone and iodine proceeds in a series of steps as follows: CH 3 COCH 3 + H 3 O + CH 3 C(OH) + CH 3 + H 2 O CH 3 C(OH) + CH 3 + H 2 O CH 2 = C(OH)CH 3 + H 3 O + CH 2 = C(OH)CH 3 + I 2 CH 2 ICOCH 3 + HI slow fast fast The orders with respect to propanone, hydroxonium (H 3 O + ) and iodine which support this would be: CH 3 COCH 3 H 3 O + I 2 A 1 1 0 B 1 0 0 C 0 0 1 D 1 1 1 8 Which one of the following equimolar salt solutions would have the highest ph? A B C D ammonium chloride ammonium ethanoate sodium chloride sodium ethanoate 9 Ammonia may be oxidised by mixing it with air and passing the mixture over a heated platinum rhodium catalyst. 4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g) Assuming air to be 20% oxygen, what volume of air is needed to react completely with 10.0 dm 3 of ammonia at 20 C and 1 atmosphere pressure? A 12.5 dm 3 B 40.0 dm 3 C 50.0 dm 3 D 62.5 dm 3 A2C1S8 3606 4 [Turn over
10 Given the following half-equations E / V Br 2 (aq) + 2e 2Br (aq) +1.07 O 2 (g) + 4H + (aq) + 4e 2H 2 O(l) +1.23 S 2 O 2 8 (aq) + 2e 2SO 2 4 (aq) +2.01 which one of the following species could oxidise water to oxygen? A B C D Br (aq) Br 2 (aq) SO 2 4 (aq) S 2 O 2 8 (aq) A2C1S8 3606 5 [Turn over
Section B Answer all five questions in the spaces provided. 11 Glucose is a white crystalline solid which exhibits the reactions of an aliphatic aldehyde. Its structure can be represented as: CHO CHOH CHOH CHOH CHOH CH 2 OH (a) State what is observed when glucose is boiled with Fehling s solution. [1] (b) Glucose is optically active. (i) Explain the meaning of the term optically active. [1] (ii) How many asymmetric centres are there in a glucose molecule? [1] A2C1S8 3606 6 [Turn over
(c) Draw the structure of the product formed between glucose and 2,4-dinitrophenylhydrazine, representing glucose as RCHO. [2] (d) Fermentation of glucose produces ethanol and carbon dioxide. The reaction is catalysed by the enzyme zymase found in yeast. (i) Write an equation for the fermentation of glucose. (ii) State what effect the enzyme has on the activation energy for this reaction. [1] A2C1S8 3606 7 [Turn over
12 Nitrogen monoxide, NO, is a colourless gas which is formed in the reaction between moderately concentrated nitric acid and copper metal. In the presence of air it is immediately oxidised to the dioxide. (a) Write the equation for the formation of nitrogen monoxide from nitric acid and copper. [2] (b) The oxidation of nitrogen monoxide is represented by the equation: 2NO(g) + O 2 (g) 2NO 2 (g) The kinetics of this reaction were studied and the following results recorded. Experiment Initial concentration of NO 10 3 mol dm 3 Initial concentration of O 2 10 3 mol dm 3 Initial rate 10 4 mol dm 3 s 1 1 1 1 6 2 2 1 24 3 3 1 54 4 2 2 48 5 3 3 162 (i) Using these results, deduce the order of the reaction with respect to nitrogen monoxide and oxygen and write the overall rate equation. order with respect to NO order with respect to O 2 rate equation [3] (ii) On the axes below, sketch the shape of the graph expected in each case. [NO] rate time [NO] [2] A2C1S8 3606 8 [Turn over
(iii) Use the results for experiment 1 to determine the value of the rate constant and state its units. [3] (c) Nitrogen dioxide, NO 2, is a brown gas which dimerises to form colourless dinitrogen tetroxide, N 2 O 4. The following equilibrium is established. N 2 O 4 (g) 2NO 2 (g) ΔH = + 58 kj (i) State and explain the effect of reducing the total pressure on the above equilibrium. (ii) A sealed flask containing pure dinitrogen tetroxide was heated to 80 C and equilibrium allowed to establish. At equilibrium, the total pressure was 125 kpa and the mole fraction of dinitrogen tetroxide was found to be 0.20. Calculate the value of K p for this reaction, stating its units. [4] (iii) State and explain the effect of increasing the temperature on the value of K p. A2C1S8 3606 9 [Turn over
(d) Nitrogen dioxide dissolves in water to form an acidic solution. 2NO 2 + H 2 O HNO 3 + HNO 2 The nitrous acid decomposes to form more nitric acid. (i) Explain the relative strengths of nitrous and nitric acids. (ii) Given the half equations VO 2+ (aq) + 2H + (aq) +e V 3+ + H 2 O(l) E = +0.34 V NO 3 (aq) + 4H + (aq) + 3e NO(g) + 2H 2 O(l) E = +0.96 V VO 2 + (aq) + 2H + (aq) + e VO 2+ (aq) + H 2 O(l) E = +1.00 V deduce the equation for the reaction which occurs when nitric acid is added to a solution containing a mixture of V 3+ and VO 2+ ions. (iii) A text book notes that nitrous acid can act as both an oxidising agent and a reducing agent. With reference to oxidation number, explain this statement by referring to the reactions of the acid with acidified aqueous solutions of iron(ii) sulphate and potassium manganate(vii). [4] A2C1S8 3606 10 [Turn over
13 Using only elements from the third period of the Periodic Table, answer the following questions. (a) (i) Write the formula of the metallic chloride which contains both covalent and coordinate (dative) bonds. [1] (ii) Which element forms an oxide in which its oxidation state is +5? [1] (iii) Name the element which forms an oxide with a giant covalent structure. [1] (b) Aluminium oxide is amphoteric. (i) Explain the term amphoteric. [1] (ii) Write the equation for the reaction between aluminium oxide and sulphuric acid. A2C1S8 3606 11 [Turn over
14 Linoleic acid (octadeca-9,12-dienoic acid), is one of two essential fatty acids in our diet since our bodies are unable to synthesise it. CH 3 (CH 2 ) 4 CH = CHCH 2 CH = CH(CH 2 ) 7 COOH linoleic acid Deficiency can lead to scaly skin and hair loss. Glyceryl esters of the acid are plentiful in sunflower oil. (a) (i) The configuration at each double bond is cis. Draw the structure of linoleic acid. [1] (ii) Draw the structure of the oil formed when one molecule of glycerol reacts with three molecules of linoleic acid, representing the acid as C 17 H 31 COOH. [2] (iii) The iodine value for sunflower oil is typically in the range 125 145, while that of butter is 26 45. Explain these differences. A2C1S8 3606 12 [Turn over
(iv) Describe how the iodine value of a sample of sunflower oil may be determined. [4] Quality of written communication [2] (b) Rancidity results from the oxidation of fats and oils in the absence of enzymes. This autoxidation may be slowed down by the addition of antioxidants such as citric acid which has the structure: CH 2 COOH HO C COOH CH 2 COOH (i) Write an equation to show the reaction of citric acid with excess sodium hydroxide solution. (ii) Titration of 25.0 cm 3 of a citric acid solution required 17.5 cm 3 of 0.1 M sodium hydroxide solution. Calculate the concentration of citric acid in g dm 3. [4] A2C1S8 3606 13 [Turn over
15 Aldehydes and ketones are responsible for many familiar smells. Benzaldehyde is used to make almond essence while heptan-2-one gives blue cheese its odour. H C O CH 3 COCH 2 CH 2 CH 2 CH 2 CH 3 benzaldehyde C 6 H 5 CHO heptan-2-one (a) Fruits such as apricots contain amygdalin, C 20 H 27 O 11 N, which is hydrolysed by enzymes to form benzaldehyde, glucose and hydrogen cyanide. Write the equation for this reaction. [2] (b) Benzaldehyde reacts with hydrogen cyanide to form benzaldehyde cyanohydrin. (i) Suggest the flow scheme for the mechanism of this reaction. (ii) Name the mechanism of this reaction. [3] A2C1S8 3606 14 [Turn over
(c) Benzaldehyde may be oxidised using acidified potassium manganate(vii) to form benzoic acid, C 6 H 5 COOH. Benzoic acid is a weak acid with an acid dissociation constant, K a, of 6.3 10 5 mol dm 3. Calculate the ph of a 0.001 M solution of benzoic acid. [3] (d) (i) Explain the relative solubilities of propanone and heptan-2-one in water. (ii) Name the organic product formed when heptan-2-one reacts with lithal, LiAlH 4. [1] THIS IS THE END OF THE QUESTION PAPER A2C1S8 3606 15 [Turn over
S 4/07 529-024-1 [Turn over