Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2007 Chemistry Assessment Unit A2 1 assessing Module 4: Further Organic, Physical and Inorganic Chemistry [A2C11] A2C11 FRIDAY 25 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 13(b)(i). 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. A2C1S7 2901 For Examiner s use only Question Total Number Section A 1 10 Section B 11 12 13 14 15
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 reaction between propanone and hydrogen cyanide is described as A B C D electrophilic addition. electrophilic substitution. nucleophilic addition. nucleophilic substitution. 2 What is the ph of the buffer formed when 50 cm 3 of 0.20 M sodium hydroxide is added to 50 cm 3 0.40 M ethanoic acid? (K a of ethanoic acid = 1.75 10 5 mol dm 3 ) A 2.58 B 2.73 C 4.76 D 11.71 3 Which one of the following sets of sugars will form a silver mirror with Tollen s reagent? A Fructose, glucose and maltose B Fructose, glucose and sucrose C Fructose, maltose and sucrose D Glucose, maltose and sucrose 4 Given the following standard electrode potentials: Zn 2+ (aq) + 2e Zn(s) 0.76 V Fe 2+ (aq) + 2e Fe(s) 0.44 V I 2 (aq) + 2e 2I (aq) +0.54 V Fe 3+ (aq) + e Fe 2+ (aq) +0.77 V Which one of the following statements is correct? A Zinc metal is the most powerful oxidising agent. B Iron metal will displace iodide ions from solution. C Iron(II) ions will reduce iodine to iodide ions. D Iodide ions will reduce iron(iii) ions to iron(ii) ions but not to iron. A2C1S7 2901 2 [Turn over
5 Which one of the following represents the complex formed when thiosulphate ions are used as a fixer in photography? A B C D [Ag(S 2 O 3 ) 2 ] 3 (aq) [Ag 2 (S 2 O 3 ) 2 ] 2 (aq) [AgS 2 O 3 ] (aq) Ag 2 S 2 O 3 (s) 6 The table below shows the ph range over which some indicators change colour. Indicator ph range of colour change Salicyl yellow 10.0 12.0 Thymol blue 8.0 9.6 Bromothymol blue 6.0 7.6 Malachite green 0.2 1.8 Which one of the following indicators is suitable to establish the end point when adding 0.1 M HCl to 0.1 M NH 3? A B C D Bromothymol blue Malachite green Salicyl yellow Thymol blue 7 The partition coefficient of butanedioic acid between ethoxyethane and water is 5. What mass of butanedioic acid will be extracted when a solution containing 5.00 g of butanedioic acid in 100 cm 3 of water is shaken with 10 cm 3 of ethoxyethane? A B C D 0.50 g 1.67 g 3.33 g 4.50 g 8 Which one of the following salts dissolves in water to form an acidic solution? A B C D Ammonium chloride Lithium chloride Potassium hydrogencarbonate Sodium carbonate A2C1S7 2901 3 [Turn over
9 Which one of the following compounds displays optical isomerism? A CH 3 CHOHCOOH B CH 2 OHCH 2 COOH C CH 2 OHCOOCH 3 D CH 2 OHCH 2 CHO 10 Which one of the following is a conjugate acid-base pair? Acid Conjugate base A H 2 SO 4 HSO 4 B HSO 4 H 3 O + C SO 4 2 HSO 4 D HSO 4 H 2 SO 4 A2C1S7 2901 4 [Turn over
Section B Answer all five questions in the spaces provided. 11 Dinitrogen pentoxide (N 2 O 5 ), when heated, decomposes according to the equation: 2N 2 O 5 (g) 2N 2 O 4 (g) + O 2 (g) (a) Giving no practical details, suggest one way by which the rate of this reaction could be measured. _ [1] (b) The following results were obtained for the reaction at 45 C. Rate of [N 2 O 5 ] 10 3 mol dm 3 disappearance of N 2 O 5 10 6 mol dm 3 s 1 20.4 11.2 18.2 10.0 12.5 6.9 9.5 5.2 4.0 2.2 (i) Plot a graph of these results and deduce the rate equation for the reaction. 12 10 rate of disappearance of N 2 O 5 10 6 (mol dm 3 s 1 ) 8 6 4 2 0 0 5 10 15 20 25 [N 2 O 5 ] 10 3 (mol dm 3 ) A2C1S7 2901 5 [Turn over
(ii) Calculate the value of the rate constant, stating its units. A2C1S7 2901 6 [Turn over
12 The elements of the third period, sodium to chlorine, show a change from metallic to non-metallic character across the period. (a) Complete the table below giving the formula, classification (acidic, basic, amphoteric or neutral) and type of bonding present in each of the oxides of the elements listed. Element Formula of oxide Classification Type of bonding in oxide Aluminium Phosphorus Silicon [3] (b) Aluminium reacts with chlorine to form aluminium chloride, Al 2 Cl 6. (i) Showing the outer electrons only, draw a dot-cross diagram to show the bonding in aluminium chloride. [3] (ii) Write an equation for the reaction of aluminium chloride with water. A2C1S7 2901 7 [Turn over
(c) Magnesium reacts slowly with cold water, but will burn in steam to form magnesium oxide. (i) Draw a labelled diagram of the apparatus you could use to burn magnesium in steam. [2] (ii) The partially complete Born Haber Cycle for magnesium oxide is shown below. Mg 2+ (g) + O 2 (g) Mg 2+ (g) + O(g) + 2e Mg 2+ (g) + O 2 (g) + 2e 1 2 B Mg(g) + 1 2 O 2 (g) A Mg(s) + 1 2 O 2 (g) MgO(s) Name the changes A and B. A B [2] A2C1S7 2901 8 [Turn over
(iii) Using the data below, calculate the lattice enthalpy for magnesium oxide. kj mol 1 A +150 B +2186 Bond enthalpy for oxygen +596 1st & 2nd electron affinity for oxygen +650 Enthalpy of formation of magnesium oxide 602 A2C1S7 2901 9 [Turn over
13 Pheromones, used as a chemical communication system by insects, were first isolated and identified in 1959. (a) The isomers shown below are pheromones used by two different insects. CH 3 CH 2 CH 2 COCH 3 A (CH 3 ) 2 CHCH 2 CHO B (i) What is the systematic name for A? [1] (ii) Give a chemical test to distinguish between A and B, stating any observations you would make. [3] (iii) The cabbage white butterfly can detect as little as 1 10 13 g of B. Calculate how many molecules of B are present in 1 10 13 g. [3] A2C1S7 2901 10 [Turn over
(b) The european paper wasp uses 3-methylbutanoic acid, (CH 3 ) 2 CHCH 2 COOH, as a pheromone. (i) Explain, giving experimental details, how a pure sample of 3-methylbutanoic acid could be prepared from the alcohol, 3-methylbutan-1-ol. [4] Quality of written communication [2] (ii) The dissociation constant, K a, for 3-methylbutanoic acid is 1.5 10 3 mol dm 3. Calculate the ph of a 0.1 M solution of 3-methylbutanoic acid. (iii) Give two observations when phosphorus(v) chloride is added to 3-methylbutanoic acid. (iv) Write an equation for the reaction in part (iii). A2C1S7 2901 11 [Turn over
14 Iron Age man formed soap by boiling animal fat with water and wood ash, which is alkaline. (a) Fats are esters of propan-1,2,3-triol and fatty acids. (i) Draw the structure of the ester tristearin formed from stearic acid and propan-1,2,3-triol. [2] (ii) Write an ionic equation for the reaction of tristearin with hydroxide ions. (b) The saponification value of a fat is a measure of the relative molecular masses of the fatty acids present. (i) Define the term saponification value. (ii) The following results were obtained when the saponification value for lard was determined. Mass of lard = 1.05 g Volume of 0.1 M KOH added = 50.0 cm 3 Volume of 0.1 M HCl needed to neutralise unreacted KOH = 13.3 cm 3 Calculate the saponification value for lard. [4] A2C1S7 2901 12 [Turn over
(c) Olive oil is an unsaturated fat. The degree of unsaturation in a fat is measured using its iodine value. (i) Define the term iodine value. (ii) Olive oil may be hardened using nickel as a catalyst. Explain the chemistry of hardening. (d) Explain why nutritionists advise that our diet should be low in saturated fats. [1] A2C1S7 2901 13 [Turn over
15 Sulphuric acid was first discovered in the 8th century by the alchemist Jabir ibn Hayyan. Today it is manufactured using the Contact Process. (a) One step in the manufacture is the formation of sulphur trioxide from sulphur dioxide. 2SO 2 (g) + O 2 (g) 2SO 3 (g) (i) State the conditions used for the above reaction. Catalyst: Pressure: Temperature: [3] (ii) Explain why these conditions are used. Catalyst: Pressure: Temperature: [3] (iii) Write an expression for K p for the equilibrium. [1] A2C1S7 2901 14 [Turn over
(iv) In an experiment 2.00 moles of SO 2 and 2.00 moles of O 2 are mixed and allowed to reach equilibrium at 1100 K and 1.78 10 8 Nm 2. 1.8 moles of SO 3 were present at equilibrium. Calculate the value of K p stating its units. [4] (b) Sulphuric acid is used in the manufacture of fertilisers such as superphosphate (Ca(H 2 PO 4 ) 2 ). (i) Write an equation for the formation of superphosphate. (ii) Calculate the percentage of phosphorus in superphosphate. (iii) State one advantage and one disadvantage of using artificial fertilisers such as superphosphate. Advantage: Disadvantage: THIS IS THE END OF THE QUESTION PAPER A2C1S7 2901 15 [Turn over
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