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GCE JAN 2007 : (AS 1) General Chemistry

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education January 2007 Chemistry assessing Module 1: General Chemistry ASC11 Assessment Unit AS 1 [ASC11] THURSDAY 18 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 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. INFORMATION FOR CANDIDATES The total mark for this paper is 100. Quality of written communication will be assessed in question 13(d). 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. For Examiner s use only Question Number Section A 1 10 Section B 11 12 13 14 15 16 Total Marks ASC1W7 2739 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 types of bonding can be described as intermolecular? A B C D 2 covalent bonding hydrogen bonding ionic bonding metallic bonding Which one of the following gives the correct flame colours for each of the metal chlorides? Metal chloride CaCl2 red red green green green crimson red BaCl2 B C D red crimson green crimson Which one of the following gases occupies the largest volume at 20 C and one atmosphere pressure? A B C D 4 crimson LiCl 3 A 0.32 g of oxygen 0.44 g of carbon dioxide 0.02 g of hydrogen 0.80 g of argon Which one of the following contains hydrogen bonds? A B C D ASC1W7 ice (s) iodine (s) methane (g) quartz (s) 2739 2 [Turn over 5 The deuterium ion, 2D+, contains 1 A B C D 6 Which one of the following molecules has a shape which is influenced by a lone pair of electrons? A B C D 7 BeCl2 CO2 C2H4 NH3 Which one of the following equations represents the third ionisation energy of aluminium? A B C D 8 one proton only. one proton and one neutron only. one proton and one electron only. one proton and one neutron and one electron only. Al(g) Al+(g) Al2+(g) Al3+(g) Al3+(g) Al2+(g) Al3+(g) Al4+(g) + + + + 3e e e e The enthalpy change for the formation of ammonia is 46.2 kJ mol 1. What is the enthalpy change, in kJ, for the reaction 2NH3(g) N2(g) + 3H2(g)? A B C D ASC1W7 46.2 +46.2 92.4 +92.4 2739 3 [Turn over 9 The Pauling electronegativity values for the following elements are: hydrogen carbon chlorine oxygen fluorine 2.1 2.5 3.0 3.5 4.0 Which one of the following bonds will be the most polar? A B C D C F Cl H C H O F 10 In which one of the following atoms is the number of protons greater than the number of neutrons? A B C D ASC1W7 2H 3He 10B 238U 2739 4 [Turn over Section B Examiner Only Marks Remark Answer all six questions in the spaces provided. 11 Circle the three polar molecules in the table below. N2 2739 BF3 C2H4 H2O ASC1W7 ASC1W7 CO2 NH3 HCl CH4 5 [3] [Turn over 12 Naturally occurring bromine consists of two isotopes. The following mass spectrum shows the molecular ion region. Examiner Only Marks Remark 100 relative abundance 50 158 160 162 mass/charge (a) (i) Define the term isotope. ______________________________________________________ ____________________________________________________ [2] (ii) State the mass numbers of the two bromine isotopes. ____________________________________________________ [1] (iii) Deduce the percentage abundance of each isotope. ______________________________________________________ ____________________________________________________ [1] (b) The isotopes cannot be chemically distinguished. They both react with sodium and phosphorus in the same way to form sodium bromide and phosphorus tribromide respectively. (i) Explain why the isotopes react in the same way. ______________________________________________________ ____________________________________________________ [1] ASC1W7 2739 6 [Turn over (ii) Write the equation for the reaction of sodium with bromine. Examiner Only Marks Remark ____________________________________________________ [2] (iii) Write the equation for the reaction of phosphorus, P4, with bromine. ____________________________________________________ [2] (c) Both sodium bromide and phosphorus tribromide can be used to prepare hydrogen bromide. Hydrolysis of phosphorus tribromide yields pure hydrogen bromide gas. The reaction of sodium bromide with concentrated sulphuric acid yields an impure gas. PBr3 + 3H2O 3HBr + H3PO3 (i) Calculate the volume of hydrogen bromide produced, at 20 C and one atmosphere pressure, when 9.0 g of phosphorus tribromide are completely hydrolysed. ______________________________________________________ ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] (ii) Write the equation for the reaction of sodium bromide with concentrated sulphuric acid to form hydrogen bromide. ____________________________________________________ [2] (iii) Explain why the hydrogen bromide, prepared using sulphuric acid, is impure and name the impurities present. ______________________________________________________ ____________________________________________________ [2] (d) Hydrogen bromide decomposes at high temperatures. Name the products. _______________________________________________________ [1] ASC1W7 2739 7 [Turn over 13 The neutralisation of hydrochloric acid with potassium hydroxide can be used to illustrate Hess s Law as shown by the diagram below. Examiner Only Marks Remark H1 KOH(s) H2 +HCl(aq) KCl(aq) H3 +H2O(l) KOH(aq) (a) (i) Write the equation for the reaction of KOH(s) with HCl(aq). ____________________________________________________ [1] (ii) Define the term standard enthalpy change of neutralisation. ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] (b) (i) State Hess s Law in words. ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] (ii) Write an equation to express Hess s Law using H1, H2 and H3 from the above enthalpy cycle. ____________________________________________________ [1] ASC1W7 2739 8 [Turn over (c) What solution must be added to KOH(aq) in order to measure H3? Examiner Only Marks Remark _______________________________________________________ [1] (d) Explain how you would determine the value of H1 experimentally using 5.6 g of potassium hydroxide. __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ _______________________________________________________ [4] Quality of written communication ASC1W7 2739 [2] 9 [Turn over 14 Silver metal is valued for its appearance and its conductivity. Its electrical conductivity is greater than that of any other metal. Examiner Only Marks Remark Before 1919 British silver coinage contained 92.5% silver. At the end of 1946 silver coinage was replaced by cupro-nickel alloy coins. Silver metal will dissolve in all concentrations of nitric acid to form silver nitrate. (a) Explain the process by which silver metal conducts electricity. __________________________________________________________ _______________________________________________________ [2] (b) The equation for the reaction of silver with nitric acid is: 3Ag + 4HNO3 3AgNO3 + 2H2O + NO (i) Determine the oxidation numbers of the underlined elements in the following species from the equation and use them to explain the redox reaction taking place. Ag HNO3 AgNO3 NO ______________________________________________________ ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] (ii) Silver nitrate is amazingly soluble in hot water; 100 cm3 of boiling water dissolves 952 g of silver nitrate. Calculate the molarity of this saturated solution, assuming no change in volume from 100 cm3. ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] ASC1W7 2739 10 [Turn over (c) A coin containing silver can be dissolved in nitric acid and silver chloride, AgCl, precipitated using sodium chloride solution. After drying and weighing the mass of the precipitate is used to determine the amount of silver present in the coin. Examiner Only Marks Remark (i) Write an equation for the reaction of silver ions with chloride ions. ____________________________________________________ [1] (ii) Calculate the percentage of silver in a coin weighing 5.00 g which produces 6.11 g of silver chloride using the following headings: relative formula mass of silver chloride ______________________________________________________ percentage of silver in silver chloride ______________________________________________________ mass of silver in 6.11g of silver chloride ______________________________________________________ percentage of silver in the coin ____________________________________________________ [4] (d) The silver chloride precipitate is white when first obtained but changes its appearance if left for some time in the laboratory. (i) State the change in appearance and explain why it takes place. ______________________________________________________ ____________________________________________________ [2] (ii) Suggest why this could affect the result for the percentage determination of silver. ____________________________________________________ [1] ASC1W7 2739 11 [Turn over (e) Silver nitrate reacts with iodine as shown in the following equation. The reaction involves disproportionation. Examiner Only Marks Remark 6AgNO3(aq) + 3I2(aq) + 3H2O(l) AgIO3(aq) + 5AgI(s) + 6HNO3(aq) (i) Explain the term disproportionation. ______________________________________________________ ____________________________________________________ [1] (ii) Which element is undergoing disproportionation? ____________________________________________________ [1] (iii) Describe what would be observed. ______________________________________________________ ____________________________________________________ [2] ASC1W7 2739 12 [Turn over 15 Ammonia does not burn in air but it will burn in oxygen. Examiner Only Marks Remark (a) The equation for the combustion of ammonia in oxygen is: 4NH3(g) + 3O2(g) 2N2(g) + 6H2O(g) (i) If 20 cm3 of ammonia are reacted with the required amount of oxygen, what is the total volume of gases produced at the same temperature and pressure? ____________________________________________________ [1] (ii) Using the table of bond enthalpies below, calculate the enthalpy change for the combustion of one mole of ammonia. bond kJ mol 1 N H O O N N O H 391 498 945 464 ______________________________________________________ ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] (iii) Explain why this reaction is exothermic. ______________________________________________________ ____________________________________________________ [1] ASC1W7 2739 13 [Turn over (b) The partial oxidation of ammonia, using a platinum catalyst, is used in the manufacture of nitric acid. The equation for the catalysed oxidation of ammonia is: Examiner Only Marks Remark 4NH3 + 5O2 4NO + 6H2O This is also an exothermic reaction. Draw a labelled enthalpy level diagram for the reaction. [3] (c) Ammonia also reacts with chlorine in two different ways. Excess ammonia results in the formation of nitrogen and ammonium chloride. The following equation is not balanced. NH3 + Cl2 N2 + NH4Cl (i) Write the balanced equation and insert state symbols. ____________________________________________________ [2] (ii) Write the formulae for the ions present in ammonium chloride. ____________________________________________________ [2] ASC1W7 2739 14 [Turn over (d) Ammonia reacts with a limited amount of chlorine to form nitrogen trichloride, an extremely explosive substance. Examiner Only Marks Remark (i) Draw the dot and cross diagram for nitrogen trichloride showing outer electrons only. [2] (ii) Draw and explain the shape of a nitrogen trichloride molecule. ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] ASC1W7 2739 15 [Turn over 16 A solution of iodine in hexane can be titrated with standard sodium thiosulphate solution to determine the concentration of iodine. Examiner Only Marks Remark sodium thiosulphate solution solution of iodine in hexane (a) State the colour of iodine in hexane. _______________________________________________________ [1] (b) (i) State the indicator used, when this indicator is added to the conical flask and the colour change observed at the endpoint. ______________________________________________________ ______________________________________________________ ____________________________________________________ [3] (ii) Suggest why it is important to swirl the flask vigorously after the addition of sodium thiosulphate solution. ____________________________________________________ [1] ASC1W7 2739 16 [Turn over (c) The sodium compound produced during the titration has the following percentage composition. Examiner Only Marks Remark (i) Complete the table. Element Grams of element in 100 g of compound sodium 47.41 oxygen Ratio of moles of element 17.03 sulphur Moles of element 35.60 [2] (ii) Determine the empirical formula. ____________________________________________________ [1] (iii) Write the formula of the sodium compound. ____________________________________________________ [1] THIS IS THE END OF THE QUESTION PAPER ASC1W7 2739 17 [Turn [Turn over ASC1W7 2739 18 [Turn over ASC1W7 2739 19 [Turn over S 6/06 2300 9-058-1 [Turn over

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Additional Info : Gce Chemistry January 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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