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GCE JUN 2007 : (AS 1) General Chemistry

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2007 Chemistry assessing Module 1: General Chemistry ASC11 Assessment Unit AS 1 [ASC11] WEDNESDAY 6 JUNE, 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 seventeen 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 seven 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 1 10 Section B INFORMATION FOR CANDIDATES The total mark for this paper is 100. Quality of written communication will be assessed in Question 15(a)(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. 11 12 13 14 15 16 17 Total Marks ASC1S7 2900 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 elements has a giant covalent structure? A B C D 2 calcium carbon chlorine sulphur The mass spectrum of an element X is shown below: 100 Relative abundance 50 0 0 2 4 6 8 Mass/charge 10 12 What is the relative atomic mass of X? A B C D 3 10.2 10.5 10.8 10.9 Which one of the following molecules has a bond angle of 120 ? A B C D ASC1S7 BF3 BeCl2 H2O NH3 2900 2 [Turn over 4 A solution of a metal salt, sprayed into a Bunsen flame, gave a red colour. The same solution gave a yellow precipitate with acidified silver nitrate solution. The metal salt was A B C D 5 calcium bromide. lithium bromide. sodium iodide. strontium iodide. Given the following standard enthalpies of combustion: C(s) H2(g) CH3COOH(l) 393 kJ mol 1 286 kJ mol 1 487 kJ mol 1 What is the standard enthalpy of formation of ethanoic acid, CH3COOH(l) A B C D 6 192 192 871 871 The standard redox potentials for chlorine, bromine and iodine are: 2e Cl2(g) + Br2(g) + 2e I2(g) + 2e 2Cl (aq) 2Br (aq) 2I (aq) E /V +1.36 +1.09 +0.54 Which one of the following statements is correct? A B C D ASC1S7 When chlorine is added to a solution of iodine the brown colour disappears. When bromine is added to a solution of chloride ions the red colour disappears. When iodide ions are added to a solution of chlorine a brown colour appears. When bromide ions are added to a solution of iodide ions a red colour appears. 2900 3 [Turn over 7 0.84 g of a Group II carbonate, MCO3, reacts exactly with 20.0 cm3 of a 1.0 mol dm 3 solution of hydrochloric acid. MCO3 + 2HCl MCl2 + H2O + CO2 What is the metal, M? A B C D 8 Which one of the following molecules contains a triple bond? A B C D 9 barium beryllium calcium magnesium BF3 C2H4 N2 NH3 Which one of the following represents the electronic configuration of calcium in the ground state? A B C D 1s22p63d104s2 1s22s22p63s23p64s2 1s22s22p63s23p63d2 1s22s22p63s23p63d14s1 10 Which one of the following indicators would not be suitable for the titration listed? Acid solution Base solution Indicator A 0.1 M sulphuric acid 0.1 M sodium carbonate phenolphthalein B 0.1 M hydrochloric acid 0.1 M sodium carbonate methyl orange C 0.1 M hydrochloric acid 0.1 M sodium hydroxide methyl orange D ASC1S7 2900 0.1 M ethanoic acid 0.1 M sodium hydroxide 4 phenolphthalein [Turn over Section B Examiner Only Marks Remark Answer all seven questions in the spaces provided. 11 The possibility of life on Mars may be investigated by analysing the ratio of carbon-12 to carbon-13 in the methane found in its atmosphere. (a) (i) Complete the following table: Number of protons Number of neutrons Carbon-12 Carbon-13 [2] (ii) Explain why carbon-12 and carbon-13 are isotopes. ______________________________________________________ ___________________________________________________ [2] (b) Draw and explain the shape of methane. ___________________________________________________________ _______________________________________________________ [3] ASC1S7 2900 5 [Turn over 12 Chlorine dissolves in water and disproportionates as follows: Examiner Only Marks Remark Cl2 + H2O HCl + HOCl (a) Calculate the oxidation number of chlorine in the following molecules. (i) Cl2 ________________ (ii) HCl ________________ (iii) HOCl ________________ [3] (b) Explain the term disproportionation. ___________________________________________________________ _______________________________________________________ [2] (c) (i) Write an ionic equation for the reaction which occurs when an excess of a solution of chlorine is added to a solution of iron(II) ions. ___________________________________________________ [2] (ii) Explain whether the iron(II) is oxidised or reduced. ______________________________________________________ ___________________________________________________ [2] ASC1S7 2900 6 [Turn over (d) Fluorine reacts with phosphorus, P4, to form phosphorus trifluoride, PF3. Examiner Only Marks Remark (i) Write an equation for this reaction. ___________________________________________________ [2] (ii) Draw a dot and cross diagram to show the bonding in PF3; using outer electrons only. [2] (iii) With reference to PF3 explain the octet rule. ______________________________________________________ ___________________________________________________ [1] ASC1S7 2900 7 [Turn over 13 People who live within 50 miles of a nuclear power plant are advised to have a supply of Anti-Rad tablets readily available: Examiner Only Marks Remark Each tablet weighs 0.085 g and contains potassium iodate. In an experiment to determine the percentage of iodine in a tablet, 30 tablets were dissolved in water and added to excess acidified potassium iodide solution, producing a solution of iodine. (a) Write the equation for the reaction between iodide ions, I , and iodate ions, IO3 , in the presence of acid. _______________________________________________________ [2] (b) The iodine solution was added to a 250 cm3 volumetric flask and made up to the mark with deionised water. The number of moles of iodine were found by titration of 25.0 cm3 portions against 0.02 mol dm 3 sodium thiosulphate solution. (i) Write the equation for the reaction between iodine, I2, and sodium thiosulphate, Na2S2O3. ___________________________________________________ [2] (ii) Suggest a suitable indicator for the reaction and state when it should be added to the titration flask. ______________________________________________________ ___________________________________________________ [2] ASC1S7 2900 8 [Turn over (c) It was found that 22.5 cm3 of aqueous sodium thiosulphate were required to react with the 25.0 cm3 portion of iodine solution. Examiner Only Marks Remark (i) Calculate the number of moles of sodium thiosulphate used. ___________________________________________________ [1] (ii) Calculate the number of moles of iodine, I2, in 25.0 cm3 of solution. ___________________________________________________ [1] (iii) Calculate the mass of iodine in 25.0 cm3 of solution. ___________________________________________________ [1] (iv) Calculate the mass of iodine in 250 cm3 of solution. ___________________________________________________ [1] (v) Calculate the mass of iodine in one tablet. ___________________________________________________ [1] (vi) Calculate the percentage of iodine in each tablet. ___________________________________________________ [1] ASC1S7 2900 9 [Turn over 14 Sodium was first isolated by Sir Humphrey Davy in 1807 by the electrolysis of the molten hydroxide. Examiner Only Marks Remark (a) Sodium hydroxide is an ionic solid. (i) State the charge on a sodium ion. ___________________________________________________ [1] (ii) Draw a diagram of a sodium ion showing all the electrons present. [1] (iii) State the charge on a hydroxide ion. ___________________________________________________ [1] (iv) Draw a dot and cross diagram of a hydroxide ion showing the outer electrons only. [2] ASC1S7 2900 10 [Turn over (v) Explain why molten sodium hydroxide is able to conduct electricity. Examiner Only Marks Remark ___________________________________________________ [1] (vi) Write an equation for the conversion of sodium ions to sodium metal. ___________________________________________________ [1] (vii)Write an equation for the conversion of hydroxide ions to oxygen and water. ___________________________________________________ [1] (b) (i) Draw the structure of a typical metal showing the delocalised electrons present. [2] (ii) State two properties of sodium, other than conductivity, which are typical of a metal. 1. ____________________________________________________ 2. __________________________________________________ [2] ASC1S7 2900 11 [Turn over 15 (a) Potassium hydroxide may be converted to potassium chloride by neutralisation with hydrochloric acid. Examiner Only Marks Remark (i) Write the equation for this reaction. ___________________________________________________ [1] (ii) Briefly describe how the enthalpy of neutralisation of this reaction may be determined. Give experimental details, including one source of error and one safety precaution. Details of calculations involved are not required. ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ___________________________________________________ [4] Quality of written communication [2] (iii) Explain the term enthalpy of neutralisation. ______________________________________________________ ___________________________________________________ [2] (b) (i) Using s,p,d notation, write the electron arrangement for the potassium ion and the chloride ion. Potassium ion __________________________ Chloride ion __________________________ ASC1S7 2900 [1] [1] 12 [Turn over (ii) Draw an s and a p orbital on the axes below: Examiner Only Marks s orbital Remark p orbital [2] (c) When a solution of potassium chloride is sprayed into a flame a lilac colour is observed. Use a labelled energy level diagram to explain the origin of this colour. [3] ASC1S7 2900 13 [Turn over 16 The melting points of the elements in the third period are shown below: Examiner Only Marks Remark 1683 K 922 K 933 K 803K 371 K Na 393K Mg Al Si P S 172K 84K Cl Ar (a) (i) Explain why the melting point of silicon is much higher than that of aluminium. ______________________________________________________ ___________________________________________________ [2] (ii) Explain why the melting point of sulphur is much higher than that of argon. ______________________________________________________ ___________________________________________________ [2] ASC1S7 2900 14 [Turn over (b) The atomic radii of the elements in the third period are shown on the graph below: Examiner Only Marks Remark 0.20 0.18 0.16 Atomic radius/nm 0.14 0.12 0.10 0.08 Na Mg Al Si P Element S Cl Ar Explain the trend. ___________________________________________________________ _______________________________________________________ [2] (c) The chart below shows the atomic and ionic radii of the elements in Group VII: 300 Cl 200 F Radius/nm 100 Br F Br Cl I I 0 (i) Explain the size of the bromine atom relative to the bromide ion. ______________________________________________________ ___________________________________________________ [1] (ii) Explain the increase in atomic radius from fluorine to iodine. ______________________________________________________ ___________________________________________________ [2] ASC1S7 2900 15 [Turn over (d) The electronegativities of the Group VII elements decrease down the group. Examiner Only Marks Remark (i) Explain the term electronegativity. ______________________________________________________ ___________________________________________________ [2] The electronegativities of hydrogen, boron and fluorine are 2.2, 2.0 and 4.0 respectively. (ii) Using these values, explain why hydrogen fluoride is polar. ______________________________________________________ ___________________________________________________ [1] (iii) Explain why, even though the boron fluoride bond is polar, the boron trifluoride molecule is non-polar. ______________________________________________________ ___________________________________________________ [2] ASC1S7 2900 ASC1S7 16 [Turn over 17 The graph below shows the first ionisation energies for the first twelve elements: Examiner Only Marks Remark Ionisation energy 1 5 10 Atomic number (a) Explain why element atomic number 8 has a lower first ionisation energy than element 7. _______________________________________________________ [1] (b) Explain why elements 3 and 11 have low values. _______________________________________________________ [1] (c) Explain why elements 2 and 10 have high values. _______________________________________________________ [1] (d) Write the equation, including state symbols, for the first ionisation energy for element number 4 (beryllium). _______________________________________________________ [2] THIS IS THE END OF THE QUESTION PAPER ASC1S7 2900 17 [Turn over ASC1S7 2900 18 [Turn over ASC1S7 2900 19 [Turn over Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. S 9/06 7-128-1

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Additional Info : Gce Chemistry June 2007 Assessment Unit AS 1Module 1: General Chemistry
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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