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GCE MAY 2006 : (A2 1) Further Organic, Physical and Inorganic Chemistry

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2006 assessing Module 4: Further Organic, Physical and Inorganic Chemistry A2C11 Chemistry Assessment Unit A2 1 [A2C11] WEDNESDAY 31 MAY, AFTERNOON 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. For Examiner s use only Question Number Marks Section A INFORMATION FOR CANDIDATES 1 9.2.06BP The total mark for this paper is 90. Quality of written communication will be assessed in question 11(d)(ii). 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. 1 10 Section B 11 12 13 14 15 Total Marks A2C1S6 2093 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 Which one of the following always has units? A B C D 2 Kw Kp pH pKa Methanol is synthesised by reacting carbon monoxide with hydrogen. CO + 2H2 CH3OH H = 91 kJ mol 1 A temperature of 250 C and a pressure of 50 atmospheres is used along with a copper catalyst. Which one of the following changes in these conditions would increase the yield of methanol? A B C D 3 increase in temperature decrease in temperature increase in mass of catalyst decrease in pressure A mixture of potassium bromide and potassium sulphate contains 5 mol of potassium ions and 2 mol of bromide ions. How many moles of sulphate ions are present? 1.5 2.0 2.5 3.0 1 9.2.06BP A B C D A2C1S6 2093 2 [Turn over 4 The following equilibrium is established when hydrogen fluoride is added to water at 25 C. HF(aq) H+(aq) + F (aq) If the concentrations of HF(aq) and F (aq) at equilibrium are 0.0077 mol dm 3 and 0.0023 mol dm 3 respectively, which one of the following is the value of the equilibrium constant? A B C D 5 1.45 103 mol dm 3 1.45 10 3 mol dm 3 6.87 10 4 mol dm 3 6.87 10 9 mol dm 3 The equation for the reaction of alkali with bromobutane is: C4H9Br + KOH C4H9OH + KBr The rate equation for the reaction is rate = k[C4H9Br] The units of the rate constant are A B C D 6 mol. mol 1. s. s 1. In which one of the following reactions is the underlined compound acting as an acid? NaH + H2O NH3 + H2O H2O + HCO 3 H2O + HPO 2 4 NaOH + H2 NH+ + OH 4 2 + H O+ CO 3 3 H2PO + OH 4 1 9.2.06BP A B C D A2C1S6 2093 3 [Turn over 7 A substance gave an orange precipitate with 2,4-dinitrophenylhydrazine and it also reduced acidified potassium manganate(VII). To which class of compounds does it belong? A B C D 8 alkene aldehyde ketone ester The number of stereoisomers of a compound with the structure CH3CHBrCH CH2 is geometric (cis-trans) A B C D 9 0 0 2 2 optical 0 2 0 2 The variation in strength of an acid is related to oxidation number. Which one of the following acids is the weakest? A B C D H2SO4 HClO4 HClO HPO3 10 A mixture of nitrogen and hydrogen, initially in the molar ratio 1:3, reached equilibrium with ammonia when 50% of the nitrogen had reacted. If the total pressure was P what is the partial pressure of ammonia in the equilibrium mixture? P/8 P/6 P/4 P/3 1 9.2.06BP A B C D A2C1S6 2093 4 [Turn over BLANK PAGE 1 9.2.06BP (Section B starts overleaf) A2C1S6 2093 5 [Turn over Section B Examiner Only Marks Remark Answer all five questions in the spaces provided. 11 Cinnamaldehyde is a yellow liquid which boils at 252 C and is obtained from cinnamon oil. In the oil it has a trans structure. H CHO CC H cinnamaldehyde (a) Suggest how you would obtain cinnamaldehyde from cinnamon oil. _______________________________________________________ [2] (b) Draw the structure of the cis form of cinnamaldehyde. [1] (c) Complete the following reactions of cinnamaldehyde by writing the structures of the organic products. HCN CHO H LiAlH4 CC H [O] 1 9.2.06BP [3] A2C1S6 2093 6 [Turn over (d) Cinnamaldehyde can be identified by reaction with 2,4-dinitrophenylhydrazine, to form a hydrazone. Examiner Only Marks Remark (i) Write the equation for this reaction showing the full structure of the hydrazone. [3] (ii) Explain how you would prepare a sample of the purified hydrazone from cinnamaldehyde and use it to confirm the identify of the aldehyde. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ ____________________________________________________ [4] Quality of written communication [2] (e) Cinnamaldehyde undergoes an addition reaction with bromine. (i) Write an equation for the reaction. ____________________________________________________ [1] (ii) Explain if the molecule produced contains any asymmetric centres. 1 9.2.06BP _______________________________________________________ ____________________________________________________ [1] A2C1S6 A2C1S6 2093 7 [Turn [Turn over 12 Sodium nitrite is used as a preservative in a variety of food products especially sausage meat. The amount present can be determined by titration with potassium permanganate. Examiner Only Marks Remark 2MnO + 5NO + 6H+ 2Mn2+ + 3H2O + 5NO 2 3 4 (a) (i) Using oxidation numbers, explain why this reaction is a redox reaction. _______________________________________________________ _______________________________________________________ ____________________________________________________ [3] (ii) In an experiment, all the sodium nitrite present in 1 kg of sausage meat was extracted using distilled water and the solution concentrated to 50 cm3. The solution was placed in a burette and titrated against 25.0 cm3 of acidified 0.02 M potassium manganate(VII) solution. 10.5 cm3 of the solution was required to reach the end point. Calculate the percentage by mass of sodium nitrite present in the sausage meat. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ ____________________________________________________ [4] (b) Sodium nitrite also acts as a reducing agent with bromine water which is decolourised forming an acidic solution of bromide and nitrate ions. Write an ionic equation for the reaction. 1 9.2.06BP _______________________________________________________ [1] A2C1S6 2093 8 [Turn over (c) Sodium nitrite reacts with dilute mineral acids to form nitrous acid which is a weakly ionised, unstable acid known only in solution. Examiner Only Marks Remark (i) Write an equation for the formation of nitrous acid from sodium nitrite using dilute sulphuric acid. ____________________________________________________ [1] (ii) The dissociation constant of nitrous acid is 4.5 10 4 mol dm 3 at room temperature. Calculate the pH of a 0.1 M solution of nitrous acid. _______________________________________________________ _______________________________________________________ ____________________________________________________ [3] (d) A mixture of sodium nitrite and nitrous acid could act as a buffer solution but in practice is of no use because of the instability of nitrous acid. (i) Explain the term buffer solution. _______________________________________________________ ____________________________________________________ [2] (ii) Calculate the pH of a solution which is 0.1 mol dm 3 with respect to nitrous acid and 0.2 mol dm 3 with respect to sodium nitrite. _______________________________________________________ _______________________________________________________ _______________________________________________________ 1 9.2.06BP ____________________________________________________ [2] A2C1S6 2093 9 [Turn over 13 The lattice enthalpy of caesium chloride can be determined using a Born Haber cycle. The table lists the data required. Examiner Only Marks Remark kJ mol 1 Enthalpy change A lattice enthalpy of CsCl B atomisation of caesium +76 C atomisation of chlorine +122 D 1st ionisation energy of caesium +376 E 1st electron affinity of chlorine 349 F enthalpy of formation of CsCl 443 (a) (i) A Born Haber cycle is shown below. Put the letter for each enthalpy change in the appropriate box. [2] (ii) Calculate the lattice enthalpy of caesium chloride. _______________________________________________________ 1 9.2.06BP ____________________________________________________ [2] A2C1S6 2093 10 [Turn over (b) Caesium chloride is the most soluble of all the Group I halides; 185.8 g of the salt dissolves in 100 cm3 of water at 25 C. Examiner Only Marks Remark (i) Calculate the molarity of this solution. _______________________________________________________ _______________________________________________________ ____________________________________________________ [3] (ii) A solution of caesium chloride is neutral although ammonium chloride is acidic. Explain why the pH values of their solutions are different. _______________________________________________________ _______________________________________________________ ____________________________________________________ [2] (c) The relative atomic mass of caesium was originally determined by precipitating silver chloride from a solution of caesium chloride using silver nitrate solution. (i) Write an ionic equation for the reaction. ____________________________________________________ [1] (ii) If 5.733 g of silver chloride were obtained from 6.734 g of caesium chloride, calculate the relative atomic mass of caesium. (Ag = 107.87 and Cl = 35.45) _______________________________________________________ _______________________________________________________ _______________________________________________________ 1 9.2.06BP ____________________________________________________ [3] A2C1S6 2093 11 [Turn over 14 Oleic acid has the structure C17H33COOH and reacts with glycerol to form the oil triolein. Examiner Only Marks Remark (a) (i) Three molecules of oleic acid react with one molecule of glycerol to form triolein. Write the equation for the reaction. ____________________________________________________ [2] (ii) Triolein is a liquid at room temperature. Explain how it may be hardened . _______________________________________________________ ____________________________________________________ [2] (b) The saponification value of an oil is the number of mg of potassium hydroxide needed to saponify 1 g of an oil. (i) Explain the term saponification. _______________________________________________________ 1 9.2.06BP ____________________________________________________ [1] A2C1S6 2093 12 [Turn over (ii) Calculate the saponification value of olive oil from the following data: Examiner Only Marks Remark 0.5 g of olive oil was placed in a round bottomed flask and 50 cm3 of 0.1 M ethanolic potassium hydroxide added. The flask was fitted with a reflux condenser and the mixture boiled for about 45 minutes by which time the solution was clear. The solution was then titrated with 0.1 M hydrochloric acid to determine the unreacted potassium hydroxide. The titre value was 23.5 cm3. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ ____________________________________________________ [3] (c) Beeswax is not a triglyceride; it is a mixture of simple esters formed from straight chain acids and straight chain alcohols. One of the esters present in beeswax is C25H51CO2C30H61. (i) Write the molecular formula for this ester. ____________________________________________________ [1] (ii) Write the empirical formula for this ester. ____________________________________________________ [1] (iii) Write the equation for the formation of this ester from the corresponding alcohol and acid. ____________________________________________________ [2] (iv) Write the equation for the hydrolysis of this ester using aqueous sodium hydroxide. ____________________________________________________ [2] 1 9.2.06BP (v) Beeswax has a melting point of 60 82 C. Explain why the melting point is not sharp. _______________________________________________________ ____________________________________________________ [1] A2C1S6 2093 13 [Turn over 15 Phosphoric acid may be prepared in the laboratory by oxidising red phosphorus with concentrated nitric acid. Examiner Only Marks Remark P4 + 10HNO3 + H2O 4H3PO4 + 5NO2 + 5NO (a) Explain why the preparation should be carried out in a fume cupboard. _______________________________________________________ [1] (b) The phosphoric acid formed is a syrupy liquid which dissolves easily in water. It reacts with alkalis to form salts. (i) Write an equation for the formation of sodium dihydrogen phosphate. ____________________________________________________ [1] (ii) Write an equation for the formation of diammonium hydrogen phosphate, (NH4)2HPO4. ____________________________________________________ [1] (iii) Calculate the percentage of nitrogen in diammonium hydrogen phosphate. _______________________________________________________ _______________________________________________________ ____________________________________________________ [2] (iv) Explain why diammonium hydrogen phosphate is used as a fertiliser. _______________________________________________________ 1 9.2.06BP ____________________________________________________ [2] A2C1S6 2093 14 [Turn over (c) Phosphoric acid is used to prepare hydrogen iodide from sodium iodide. Compare and contrast the reaction of sodium iodide with concentrated sulphuric and concentrated phosphoric acid. Examiner Only Marks Remark __________________________________________________________ __________________________________________________________ _______________________________________________________ [2] 1 9.2.06BP THIS IS THE END OF THE QUESTION PAPER A2C1S6 2093 15 [Turn over 1 9.2.06BP S 2/06 4200 302507(152) [Turn over

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Additional Info : Gce Chemistry May 2006 Assessment Unit A2 1 Module 4: Further Organic, Physical and Inorganic Chemistry
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