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GCE JUN 2008 : (AS 1) General Chemistry

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2008 Chemistry assessing Module 1: General Chemistry ASC11 Assessment Unit AS 1 [ASC11] WEDNESDAY 4 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 sixteen 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 six 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 INFORMATION FOR CANDIDATES The total mark for this paper is 100. Quality of written communication will be assessed in Question 14(b). In Section A all questions carry equal marks, i.e. two marks for each question. In Section B the gures 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. Section B 11 12 13 14 15 16 Total Marks ASC1S8 3532 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 An element X has 3 electrons in its outermost shell. Element Y has 6 electrons in its outermost shell. What is the empirical formula of the compound formed when X and Y combine? A B C D 2 Which one of the following equations represents a redox reaction? A B C D 3 2NH3 N2 + 3H2 CuO + H2SO4 CuSO4 + H2O H2O + H+ H3O+ AgNO3 + KI KNO3 + AgI Chlorine exists as isotopes, 35Cl and 37Cl, resulting in a relative atomic mass of 35.5. Which one of the following statements is correct? A B C D 4 XY2 X2Y X2Y3 X3Y2 The isotopes have different chemical properties. The 37Cl isotope has a natural abundance of 75%. The mass spectrum of molecular chlorine, Cl2, includes peaks at m/e 70, 72 and 74. The nuclei of the two isotopes have the same number of neutrons. Which one of the following represents the electronic structure for the V2+ ion in the ground state? A B C D ASC1S8 1s22s22p63s23p63d3 1s22s22p63s23p63d24s1 1s22s22p63s23p63d14s2 1s22s22p63s23p64s24p1 3532 2 [Turn over 5 A metal chloride solution reacts with aqueous sodium hydroxide according to the equation: MClx + xNaOH M(OH)x + xNaCl 10.0 cm3 of 0.5 M MClx solution reacted with 7.5 cm3 of 2M sodium hydroxide. What is the formula of the metal chloride? A B C D 6 MCl MCl2 MCl3 MCl4 Which one of the following correctly shows the trends in atomic radii across and down the Periodic Table? A B increase increase increase C D increase increase 7 increase increase increase Which one of the following gives the correct colour of the solution formed when the named substance is dissolved in the named solvent? substance iron(II) chloride water red brown B potassium bromide water colourless C iodine hexane brown D 3532 colour A ASC1S8 solvent chlorine hexane purple 3 [Turn over 8 Which one of the following statements is correct? A B 500 cm3 of 1M copper(II) nitrate, Cu(NO3)2, solution contains 3.0 1023 nitrate ions. C 256 g of rhombic sulphur contains 6.0 1023 S8 rings. D 9 24 dm3 of hydrogen gas, H2, at 20 C and 1 atmosphere contains 2.4 1024 atoms of hydrogen. 1 mole of sodium hydrogensulphate, NaHSO4, dissolves in water to form 1.8 1024 ions. Given the following bond enthalpies: bond bond enthalpy/kJ mol 1 C C C == C C O C H O H +347 +612 +358 +413 +464 What is the standard enthalpy change for the hydration of ethene? C2H4 + H2O C2H5OH A B C D 42 kJ mol 1 +42 kJ mol 1 254 kJ mol 1 +254 kJ mol 1 10 Which one of the following is not produced in the reaction between concentrated sulphuric acid and sodium iodide at room temperature? A B C D ASC1S8 I2 HI NaHSO4 SO3 3532 4 [Turn over Section B Examiner Only Marks Remark Answer all six questions in the spaces provided. 11 (a) On the Periodic Table below label the s, p and d blocks. [2] (b) Complete the table below indicating whether the elements represented by the letters X, Y and Z belong to the s, p or d blocks. Atom/ion Electronic structure X 1s22s22p63s23p63d34s2 Y2 1s22s22p63s23p6 Z+ s, p or d block 1s22s22p63s23p6 [3] (c) Explain why sodium, an s block element, has a lower rst ionisation energy than chlorine, a p block element. ___________________________________________________________ ___________________________________________________________ _______________________________________________________ [2] (d) (i) Draw the shape of an s orbital. [1] (ii) Draw the shape of a p orbital. [1] ASC1S8 3532 5 [Turn over 12 Nitrogen is a colourless, odourless, unreactive gas which has the formula, N2. It will react with hydrogen to a small extent if an electric discharge is passed through a mixture of nitrogen and hydrogen. Examiner Only Marks Remark (a) Nitrogen gas is believed to be unreactive because it has a triple bond. (i) In terms of electrons, what is meant by a triple bond? ______________________________________________________ ___________________________________________________ [2] (ii) Why does the presence of a triple bond explain the lack of reactivity of nitrogen? ______________________________________________________ ___________________________________________________ [1] (iii) Draw the structure of ethyne, C2H2, which contains a triple bond. Show all the bonds present. [1] (b) Nitrogen reacts with hydrogen in the presence of an iron catalyst to give a reasonable amount of ammonia. The equation for the reaction is: N2 + 3H2 M 2NH3 H = 58 kJ (i) Using the value of the enthalpy change, explain whether the reaction is exothermic or endothermic. ______________________________________________________ ___________________________________________________ [1] ASC1S8 3532 6 [Turn over (ii) On the axes below, draw an enthalpy level diagram for the reaction. Label the y-axis. Extent of reaction Examiner Only Marks Remark [3] (c) Ammonia reacts with acids to form the ammonium ion. In this the ammonia molecule reacts with a hydrogen ion to form a dative bond. (i) Write an equation for the formation of the ammonium ion. ___________________________________________________ [1] (ii) Using a dot and cross diagram, draw the structure of the ammonium ion. [2] (iii) Circle the dative bond in your structure. ASC1S8 3532 7 [1] [Turn over 13 Hydrogen is the most abundant element in the Universe. It is dif cult to place hydrogen in the Periodic Table, because it is similar to Group I and Group VII elements, being neither strongly electropositive, nor electronegative. Examiner Only Marks Remark (a) The existence of hydrogen in distant stars has been determined by spectroscopic analysis. The Lyman series (ultraviolet region) in the atomic line emission spectrum for hydrogen is shown below. A B frequency (i) With reference to speci c energy levels, explain the origin of the line labelled A. ______________________________________________________ ______________________________________________________ ___________________________________________________ [3] (ii) The line, B, may be used to determine the ionisation energy for atomic hydrogen. Write an equation, including state symbols, for the ionisation of a hydrogen atom. ___________________________________________________ [2] (b) The boiling points of the Group V hydrides are shown below: boiling point/ C NH3 SbH3 AsH3 PH3 ASC1S8 3532 8 [Turn over (i) The electronegativity values for nitrogen, phosphorus and hydrogen are 3.0, 2.1 and 2.1 respectively. Explain what is meant by the term electronegativity. Examiner Only Marks Remark ______________________________________________________ ___________________________________________________ [2] (ii) Explain why ammonia has a much higher boiling point than phosphine, PH3, naming the intermolecular forces present between molecules in the liquid phase in each case. ______________________________________________________ ___________________________________________________ [2] (iii) Phosphine has the following structure. H P H H State and explain the shape of the phosphine molecule. ______________________________________________________ ______________________________________________________ ___________________________________________________ [3] (iv) Phosphine may be produced in the laboratory by the action of water on calcium phosphide, Ca3P2. Calcium hydroxide is also produced. Write an equation for this reaction. ___________________________________________________ [2] ASC1S8 3532 9 [Turn over (c) The Group VII hydrides are gaseous at room temperature and pressure, dissolving in water to form acidic solutions. Examiner Only Marks Remark (i) Place the hydrides HF, HCl, HBr and HI in order of increasing hydrogen halogen bond strength (weakest rst). ___________________________________________________ [1] (ii) Which one of the 1M solutions of the acids HF, HCl, HBr and HI has the highest pH? ___________________________________________________ [1] (d) Many metallic hydrides such as sodium hydride, NaH, are ionic solids. (i) Show the formation of a sodium ion, Na+, and a hydride ion, H , from their atoms. [2] (ii) State and explain the relative sizes of a hydrogen atom and a hydride ion. ______________________________________________________ ______________________________________________________ ___________________________________________________ [2] (iii) Sodium hydride reacts with water to form sodium hydroxide solution and hydrogen gas. Write an equation for this reaction, including state symbols. ___________________________________________________ [2] (iv) Explain why sodium hydroxide solution conducts electricity. ______________________________________________________ ___________________________________________________ [2] ASC1S8 3532 10 [Turn over 14 Barium ferrate, BaFeO4, may be prepared by bubbling chlorine gas through a suspension of iron(III) hydroxide in potassium hydroxide solution at 70 C. The mixture is ltered and aqueous barium chloride is added to the ltrate to precipitate out barium ferrate which collects as red crystals. Examiner Only Marks Remark (a) Deduce the oxidation number of iron in the FeO42 ion and use this to explain the role of chlorine in the reaction. _________________________________________________________ ______________________________________________________ [2] (b) Using a named silver salt, describe how you would test for the presence of chloride ions in the solution remaining after separation of the crystalline product, writing an ionic equation for the reaction. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [4] Quality of written communication [2] (c) State the ame colour expected when barium ferrate solution is sprayed into a ame. Assume the presence of iron does not affect the colour. ______________________________________________________ [1] (d) Ferrate ions react with acid to produce oxygen gas. Describe a test for oxygen. _________________________________________________________ ______________________________________________________ [2] ASC1S8 3532 11 [Turn over (e) The concentration of barium ferrate in solution may be determined in the following way: passing the chlorine formed through excess potassium iodide solution to produce iodine Remark treatment with excess hydrochloric acid to liberate chlorine gas Examiner Only Marks titrating the iodine formed with standard sodium thiosulphate solution: 2Na2S2O3(aq) + I2(aq) Na2S4O6(aq) + 2NaI(aq) (i) State what is observed when chlorine gas is bubbled through potassium iodide solution. ______________________________________________________ ___________________________________________________ [2] (ii) Name the indicator used for the titration and state the colour change at the end point. ______________________________________________________ ___________________________________________________ [3] (iii) In an experiment, 25.0 cm3 of a barium ferrate solution was treated with excess hydrochloric acid and the resultant chlorine passed through excess potassium iodide solution. The iodine liberated required 23.45 cm3 of 0.1M sodium thiosulphate for complete reaction. Calculate the concentration of barium ferrate in the original solution in mol dm 3. 1 mole of ferrate ions is equivalent to 3 moles of thiosulphate ions. Number of moles of thiosulphate used: ______________________________________________________ Number of moles of barium ferrate in 25.0 cm3 of solution: ______________________________________________________ Concentration of barium ferrate in mol dm 3: ___________________________________________________ [3] ASC1S8 3532 12 [Turn over 15 The reaction between zinc and copper(II) sulphate solution is exothermic and is represented by the following equation: Examiner Only Marks Remark Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s) (a) Apart from a temperature rise, give two observations which could be made. _________________________________________________________ ______________________________________________________ [2] (b) The enthalpy change for this reaction may be estimated by adding a known mass of zinc powder to a known volume of standard copper(II) sulphate solution in a polystyrene cup and measuring the temperature rise. A spatula measure of zinc powder was added to a polystyrene cup containing 75.0 cm3 of aqueous copper(II) sulphate at 20.5 C. The temperature rose to 33.7 C. The copper metal formed was collected, washed, dried and found to weigh 0.42 g. Calculate the enthalpy change for this reaction in kJ per mole of copper formed using the following headings. (Assume the energy required to raise 1 cm3 of solution by 1 C is 4.2 J) temperature rise: ______________________________________________________ energy released in joules: ______________________________________________________ moles of copper formed: ______________________________________________________ energy released per mole of copper in kJ: ___________________________________________________ [4] ASC1S8 3532 13 [Turn over 16 Phosphorus pentachloride, PCl5, is a pale yellow solid which sublimes above 160 C and fumes in moist air forming phosphorus oxychloride, POCl3, and hydrogen chloride. Examiner Only Marks Remark Phosphorus pentachloride may be prepared in the laboratory using the apparatus below. anhydrous calcium chloride tube phosphorus trichloride dry chlorine freezing mixture of ice and water phosphorus pentachloride (a) (i) Suggest the function of the anhydrous calcium chloride tube. ___________________________________________________ [1] (ii) State one essential safety precaution for this preparation. ___________________________________________________ [1] (iii) Suggest why the reaction vessel must be cooled. ___________________________________________________ [1] (iv) Write the equation for the reaction between phosphorus trichloride and chlorine gas. ___________________________________________________ [1] (b) (i) State the Octet Rule. ___________________________________________________ [1] (ii) Suggest why PCl5 does not obey the Octet Rule. ___________________________________________________ [1] ASC1S8 3532 14 [Turn over (c) Phosphorus pentachloride reacts with oxalic acid, H2C2O4, to form phosphorus oxychloride as shown in the equation: Examiner Only Marks Remark H2C2O4(s) + PCl5(s) POCl3(s) + 2HCl(g) + CO2(g) + CO(g) (i) Suggest why this reaction is often used to synthesise pure phosphorus oxychloride. ___________________________________________________ [1] (ii) Phosphorus oxychloride is readily hydrolysed by water according to the equation: POCl3 + 3H2O H3PO4 + 3HCl Calculate the volume of hydrogen chloride gas formed, at 20 C and 1 atmosphere pressure, when 1.53 g of phosphorus oxychloride is hydrolysed. ______________________________________________________ ______________________________________________________ ___________________________________________________ [3] THIS IS THE END OF THE QUESTION PAPER ASC1S8 3532 15 [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 noti ed. S 4/07 530-049-1 16 [Turn over

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Additional Info : Gce Chemistry June 2008 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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