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GCE JAN 2008 : (A2 1) Further Organic, Physical and Inorganic Chemistry

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education January 2008 Chemistry Assessment Unit A2 1 Module 4: Further Organic, Physical and Inorganic Chemistry A2C11 assessing [A2C11] THURSDAY 10 JANUARY, 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 in 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 answer in the spaces provided in this question paper. For Examiner s use only Question Number Marks Section A 1 10 Section B INFORMATION FOR CANDIDATES The total mark for this paper is 90. Quality of written communication will be assessed in question 11(a). 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. A2C1W8 3542 11 12 13 14 15 Total Marks 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 is the correct formula for 4-chloro-2-methylpent-2-enoic acid? A B C D 2 CH3CCl=CHCH(CH3)COOH (CH3)2C=CHCHClCOOH CH3CH2CCl=C(CH3)COOH CH3CHClCH=C(CH3)COOH The oxidation of ethanedioate (oxalate) ion by acidified manganate(VII) ions can be represented by the following equations. C2O42 (aq) 2CO2(g) + 2e MnO4 + 8H+ + 5e Mn2+ + 4H2O What volume of 0.02 M potassium manganate(VII) is required to oxidise completely a solution containing 0.02 mole of ethanedioate ions? A B C D 3 40 cm3 100 cm3 250 cm3 400 cm3 In which one of the following reactions does hydrogen behave as an oxidising agent? A B C D A2C1W8 H2 + Cl2 2HCl N2 + 3H2 2NH3 C2H4 + H2 C2H6 2Na + H2 2NaH 3542 2 [Turn over 4 Which one of the following oxides is amphoteric? A B C D 5 A mixture of 8.4 g of ethene and 5.6 g of but-1-ene in a closed vessel has a total pressure of 100 kPa. What is the partial pressure of ethene? A B C D 6 Al2O3 Cl2O7 P4O10 SiO2 40 kPa 50 kPa 60 kPa 75 kPa Given the half cell reactions: Mn2+(aq) + 2e Ag+(aq) + e Mn(s) Ag(s) 1.18 V +0.80 V What is the e.m.f. of the cell? A B C D 7 0.38 V 1.98 V 2.78 V 3.16 V 3.6 g of magnesium metal were added to an excess of a solution of an arsenic compound containing Asn+ and 7.5 g of arsenic were deposited. What is the oxidation number of arsenic in the compound? A B C D A2C1W8 +2 +3 +4 +5 3542 3 [Turn over 8 Which one of the following pairs of structures are chiral isomers? H A H C C H Cl Cl CH3 Cl H B CH3 CC H H CH3 OH OH C C H C COOH HOOC CH3 CH3 H CH3CH2 C CH3 H3C C CH2CH3 CH3 9 H H D Cl CC H CH3 H CH3 The rate of the reaction: 2H2(g) + 2NO(g) 2H2O(g) + N2(g) is first order with regard to H2 and second order with respect to NO. What are the units for the rate constant? A B C D A2C1W8 mol2 dm 6 s mol 2dm6 s 1 mol dm 3 s 1 mol 1 dm3 s 3542 4 [Turn over 10 The diagram shows data for the neutralisation of 100 cm3 of hydrochloric acid with sodium hydroxide solution of equal concentration. pH 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1M 0.1 M 0.01 M 0.01 M 0.1 M 1M 98 99 100 101 102 Volume of sodium hydroxide added/cm3 Which one of the following indicators would not be suitable for a titration of a given solution of hydrochloric acid (about 0.1 M) with sodium hydroxide solution of concentration 0.1 M ? A B C D A2C1W8 congo red chlorophenol red litmus neutral red 3542 3.0 5.0 4.8 6.4 5.0 8.0 6.8 8.0 5 [Turn over Section B Examiner Only Marks Remark Answer all five questions in the spaces provided. 11 The first step in the manufacture of nitric acid is the oxidation of ammonia. 4NH3 + 5O2 4NO + 6H2O The nitrogen(II) oxide is converted into nitric acid in succeeding steps. (a) State the conditions used in the oxidation of ammonia and, using equations, explain how nitrogen(II) oxide is converted to concentrated nitric acid. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [5] Quality of written communication [2] (b) Nitric acid reacts with copper to produce copper(II) nitrate. The oxide of nitrogen formed depends on the concentration of the nitric acid. (i) Write the equation for the reaction of nitric acid with copper to produce nitrogen(IV) oxide. __________________________________________________ [1] (ii) Write the equation for the reaction of nitric acid with copper to produce nitrogen(II) oxide. __________________________________________________ [2] A2C1W8 3542 6 [Turn over (c) Industrially, nitric acid is used in the manufacture of ammonium nitrate and in forming adipic acid for the manufacture of nylon. Examiner Only Marks Remark (i) Write the equation for the formation of ammonium nitrate. __________________________________________________ [1] (ii) State and explain the use of ammonium nitrate. _____________________________________________________ __________________________________________________ [2] (iii) Write the equation for the formation of adipic acid from cyclohexanol using [O] to represent the oxidant. __________________________________________________ [2] A2C1W8 3542 7 [Turn over 12 Calcium hydride, CaH2, is formed by the reaction of calcium with hydrogen at 150 250 C. It was manufactured under the name of Hydrolith. When added to water a large volume of hydrogen is produced from a small mass of Hydrolith. This was used as a source of hydrogen in preference to transporting heavy steel cylinders. Examiner Only Marks Remark CaH2 + 2H2O Ca(OH)2 + 2H2 (a) (i) Explain the reaction of calcium hydride with water in terms of the Br nsted Lowry theory of acids and bases. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (ii) Calculate the volume of hydrogen given off at 20 C and one atmosphere pressure when 1.0 kg of calcium hydride is added to excess water. _____________________________________________________ _____________________________________________________ _____________________________________________________ __________________________________________________ [3] (b) Calcium hydride can act as a reducing agent in a similar way to other metallic hydrides such as lithium aluminium hydride. Name two functional groups which are reduced by hydrides and state their reduction products. _________________________________________________________ ______________________________________________________ [2] A2C1W8 3542 8 [Turn over (c) Calcium hydride is an ionic solid for which a Born Haber cycle can be constructed as shown below. Examiner Only Marks Remark Ca2+(g) + 2H(g) + 2e 436 kJ mol 1 Ca2+(g) + H2(g) + 2e 144 kJ mol 1 Ca2+(g) + 2H (g) 1740 kJ mol 1 Ca(g) + H2(g) Molar lattice enthalpy 193 kJ mol 1 Ca(s) + H2(g) 189 kJ mol 1 CaH2(s) (i) Write the electron structures of the calcium and hydride ions. _____________________________________________________ __________________________________________________ [1] (ii) State the value of the H H bond enthalpy. __________________________________________________ [1] (iii) If the first ionisation enthalpy of calcium is 590 kJ mol 1, calculate the second ionisation enthalpy. __________________________________________________ [1] (iv) Calculate the standard molar lattice enthalpy of calcium hydride. _____________________________________________________ __________________________________________________ [2] A2C1W8 3542 9 [Turn over 13 Calcium hydroxyapatite, Ca10(PO4)6(OH)2, makes up 95% of tooth enamel and the remaining 5% contains proteins such as collagen. Tooth decay is caused when tooth enamel is attacked by acid in the mouth. Streptococcus mutans bacteria hydrolyse sucrose and eventually produce lactic acid. The critical pH in the mouth is between 5.2 and 5.5 when calcium ions are removed from the apatite. Examiner Only Marks Remark (a) Calculate the percentage of calcium in calcium hydroxyapatite. _________________________________________________________ _________________________________________________________ ______________________________________________________ [3] (b) Streptococcus mutans bacteria hydrolyse sucrose. (i) Explain the term hydrolyse. _____________________________________________________ __________________________________________________ [1] (ii) State another method of hydrolysing sucrose. _____________________________________________________ __________________________________________________ [2] (iii) Name the two sugars produced by the hydrolysis of sucrose. _____________________________________________________ __________________________________________________ [2] A2C1W8 3542 10 [Turn over (c) Lactic acid, CH3CHOHCOOH, has a pKa value of 3.86 at 25 C. Calculate the concentration of lactic acid in mg dm 3 present in saliva which would produce a pH of 5.2. Assume there is no buffering effect. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [4] (d) Small changes in pH in the mouth are countered by buffer systems. Explain, using equations, how the carbonic acid/hydrogencarbonate ion buffer system works. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] A2C1W8 3542 11 [Turn over 14 Biodiesel is a mixture of esters which can be made by heating a vegetable oil such as rapeseed oil with methanol in the presence of sodium hydroxide as a catalyst. The process is known as transesterification. C21H39COOCH2 C21H39COOCH Examiner Only Marks Remark CH2OH + 3CH3OH 3C21H39COOCH3 + CHOH C21H39COOCH2 biodiesel CH2OH rapeseed oil The methyl ester is used as biodiesel. (a) Deduce the number of C=C double bonds in a molecule of the triglyceride in rapeseed oil. ______________________________________________________ [1] (b) Suggest the meaning of the term transesterification. _________________________________________________________ ______________________________________________________ [1] (c) The diesel engine, as invented, was able to run on pure vegetable oil. However, modern diesel engines need a less viscous oil such as biodiesel. Suggest why biodiesel is less viscous than the triglyceride. _________________________________________________________ ______________________________________________________ [2] (d) Vegetable oils like rapeseed oil are converted into solid fats for use in the food industry. Explain the chemistry involved in this hardening process. _________________________________________________________ _________________________________________________________ ______________________________________________________ [3] A2C1W8 3542 12 [Turn over (e) One of the tests performed on oils is a titration to determine the acid value which is the number of milligrams of potassium hydroxide required to neutralise 1 g of the oil and indicates the amount of free acid present. Examiner Only Marks Remark (i) Calculate the acid value of 0.38 g of rapeseed oil dissolved in toluene (methylbenzene) and titrated against 0.1 M ethanolic potassium hydroxide solution. A titre of 24.5 cm3 was needed. _____________________________________________________ _____________________________________________________ _____________________________________________________ __________________________________________________ [3] (ii) Explain why it is necessary to shake the conical flask vigorously during the titration. _____________________________________________________ __________________________________________________ [1] (f) A typical diesel molecule obtained from crude oil has the molecular formula C16H34. (i) Write the equation for complete combustion of this hydrocarbon. __________________________________________________ [2] (ii) Explain whether you would expect the complete combustion of biodiesel to produce the same products as the complete combustion of C16H34. __________________________________________________ [1] A2C1W8 3542 13 [Turn over 15 Phosgene, COCl2, is a colourless gas which condenses readily to a liquid at 8 C. It has a pungent and suffocating smell and is highly poisonous. It was discovered in 1812 by the action of light on a mixture of carbon monoxide and chlorine which led to the name from the Greek phos (light) and gene (born). Cl O=C Cl Examiner Only Marks Remark Phosgene (a) It was originally thought that light catalysed the formation of phosgene. Explain why light is not a catalyst and suggest a more likely role of the light. _________________________________________________________ ______________________________________________________ [2] (b) Phosgene is manufactured by passing carbon monoxide and chlorine through a bed of porous carbon which acts as a catalyst. CO(g) + Cl2(g) COCl2(g) Although the reaction is exothermic, it is carried out between 50 C and 150 C. (i) Explain the effect of increased pressure on the equilibrium. _____________________________________________________ __________________________________________________ [2] (ii) Explain the choice of the temperature range 50 150 C. _____________________________________________________ __________________________________________________ [2] (iii) Suggest how phosgene can be removed from the equilibrium mixture. _____________________________________________________ __________________________________________________ [1] A2C1W8 3542 14 [Turn over (c) A mixture of carbon monoxide and chlorine is allowed to reach gaseous equilibrium in a 10 dm3 vessel. The initial mixture contained 2 mol of carbon monoxide and 5 mol of chlorine. At equilibrium, 1 mol of carbon monoxide remained. What is the equilibrium constant at the temperature of the experiment? Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [3] (d) Phosgene reacts in a similar way to acyl chlorides, RCOCl and thionyl chloride, SOCl2. Write an equation for the reaction of phosgene with ethanol. ______________________________________________________ [2] (e) (i) Using outer electrons only, draw the electronic structure of phosgene. [2] (ii) Explain the shape of a phosgene molecule, stating the approximate bond angles. _____________________________________________________ __________________________________________________ [1] THIS IS THE END OF THE QUESTION PAPER A2C1W8 3542 15 [Turn over S 2/07 302-022-1

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Additional Info : Gce Chemistry January 2008 Assessment Unit A2 1 Module 4: Further Organic, Physical and Inorganic Chemistry
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