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GCE JUN 2009 : (AS 1) General Chemistry

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2009 Chemistry assessing Module 1: General Chemistry ASC11 Assessment Unit AS 1 [ASC11] WEDNESDAY 3 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 Section A 1 10 Section B 11 INFORMATION FOR CANDIDATES The total mark for this paper is 100. Quality of written communication will be assessed in question 16(e). 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. 4975 Marks 12 13 14 15 16 17 Total Marks Section A For each of the following 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 20 cm3 of 0.3 mol dm 3 potassium hydroxide solution is exactly neutralised by A B C D 2 A positively charged particle with the electron configuration 1s22s22p6 is A B C D 3 C2H4 CO2 N2 NF3 Which one of the following sodium compounds produces a gas when treated with dilute sulphuric acid? A B C D 4975 an aluminium ion. a fluoride ion. an oxide ion. a potassium ion. Which one of the following molecules contains a triple bond? A B C D 4 10 cm3 of 0.3 mol dm 3 sulphuric acid. 10 cm3 of 0.6 mol dm 3 sulphuric acid. 20 cm3 of 0.3 mol dm 3 sulphuric acid. 20 cm3 of 0.6 mol dm 3 sulphuric acid. sodium carbonate sodium chloride sodium fluoride sodium iodide 2 [Turn over 5 Which one of the following contains the name of the reagent and that of the indicator used in an iodine titration? A B C D 6 Which one of the following electron configurations has two unpaired electrons? A B C D 7 sodium sulphate and starch sodium sulphate and methyl orange sodium thiosulphate and starch sodium thiosulphate and methyl orange 1s22s2 1s22s22p3 1s22s22p4 1s22s22p63s23p5 Which area of the Periodic Table contains elements which have only s electrons in their outer shells? B A 8 Which one of the following chloro-compounds is non-polar? A B C D 4975 CD HCl CCl4 CH3Cl CHCl3 3 [Turn over 9 Which one of the following contains a coordinate bond? Examiner Only Marks A B C D Remark N2 NH3 NH2 NH4+ 10 The enthalpy of neutralisation when an acid reacts with an alkali is, by definition, the number of kilojoules released by A B C D 4975 the formation of one mole of salt. the formation of one mole of water. the neutralisation of one mole of acid. the neutralisation of one mole of alkali. 4 [Turn over Section B Examiner Only Marks Remark Answer all seven questions in the spaces provided. 11 The electronic energy levels of atomic hydrogen are shown below. Draw an arrow on the diagram which represents the energy change associated with the lowest frequency line in the ultraviolet emission spectrum. [3] 12 The electronegativity of atoms causes bonds to be polar. Indicate the polarity of the following bonds. The first one has been completed for you. + C Cl O H Cl Br N O [3] 4975 5 [Turn over 13 The female of the American cockroach (Periplaneta americana) secretes a chemical (pheromone) of molecular formula, C11H18O2, to which the male of the species is attracted. It is reported that the male may respond to as few as 60 molecules of the pheromone. Examiner Only Marks Remark What is the mass, in grams, of these 60 molecules? Use the following headings to assist you in your calculation. relative molecular mass ____________________________________________________________ ____________________________________________________________ mass of one mole ____________________________________________________________ mass of one molecule ____________________________________________________________ ____________________________________________________________ mass of sixty molecules in grams ____________________________________________________________ __________________________________________________________ [4] 4975 6 [Turn over 14 Boron forms giant covalent structures with other elements, for example, boron nitride, BN. It is claimed that boron nitride is as hard as diamond. Examiner Only Marks Remark (a) (i) Explain why diamond is so hard. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) Explain why graphite is so soft. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (iii) State one other physical property, apart from hardness, which you would expect boron nitride to possess. ___________________________________________________ [1] 4975 7 [Turn over (b) Both boron and carbon combine with fluorine. Boron forms boron trifluoride (BF3) and carbon forms carbon tetrafluoride, (CF4). Examiner Only Marks Remark (i) Write an equation for the formation of boron trifluoride from boron and fluorine. ___________________________________________________ [2] (ii) Write an equation for the formation of carbon tetrafluoride from methane and fluorine, the other product being hydrogen fluoride. ___________________________________________________ [2] (iii) Use dot and cross notation to draw the structures of boron trifluoride and carbon tetrafluoride, showing outer electrons only. [2] (iv) Explain the octet rule and comment on its application to boron trifluoride and carbon tetrafluoride. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [4] (v) Draw the shapes of BF3 and CF4 and explain them in terms of their electron structure. _____________________________________________________ _____________________________________________________ ___________________________________________________ [4] 4975 8 [Turn over 15 Calcium fluoride, CaF2, occurs naturally as fluorite or fluorspar. Impurities give a blue variety known as Blue John. Fluorspar is the major source of hydrogen fluoride and fluorine. Examiner Only Marks Remark It can be prepared in the laboratory by precipitation or direct combination of the elements. (a) What is the colour of pure calcium fluoride? _______________________________________________________ [1] (b) Explain the formation of calcium fluoride from calcium and fluorine atoms using dot and cross diagrams showing outer electrons only. [4] (c) Write an equation for the precipitation of calcium fluoride by mixing solutions of calcium chloride and sodium fluoride. _______________________________________________________ [1] (d) Calcium fluoride reacts with concentrated sulphuric acid to form hydrogen fluoride and calcium sulphate. Write an equation for the reaction. _______________________________________________________ [2] 4975 9 [Turn over (e) Calcium fluoride is sparingly soluble in water; 0.0025 g dissolves in 100 cm3 of water at 18 C. Examiner Only Marks Remark Calculate the concentration of fluoride ions in moles per litre using the following headings: (i) relative formula mass of calcium fluoride _____________________________________________________ (ii) number of moles of calcium fluoride in 0.0025 g _____________________________________________________ (iii) number of moles of fluoride ion in 0.0025 g of calcium fluoride _____________________________________________________ (iv) number of moles of fluoride ion in 100 cm3 of water _____________________________________________________ (v) number of moles of fluoride ion in 1000 cm3 of water ___________________________________________________ [5] (f) The presence of fluoride ions in domestic water supplies is regarded as beneficial by some, but the deliberate addition of fluoride ions is controversial. (i) State one benefit of fluoride ions in drinking water. ___________________________________________________ [1] (ii) Explain why some people object to the addition of fluoride ions to drinking water. _____________________________________________________ ___________________________________________________ [1] 4975 10 [Turn over 16 All naturally occurring sodium atoms have a relative atomic mass of 23 i.e. the atoms are represented by the symbol 23Na. However, radioactive isotopes of sodium, e.g. 24Na, may be prepared. Examiner Only Marks Remark (a) (i) State the number of electrons, protons and neutrons in an atom of 23Na. _____________________________________________________ ___________________________________________________ [2] (ii) Explain why 23Na and 24Na are regarded as isotopes. _____________________________________________________ ___________________________________________________ [2] (b) A sample of sodium from a nuclear reactor contains 2.00% of 24Na and 98.00% of 23Na by mass. Calculate the relative atomic mass of the sample to two decimal places. _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] 4975 11 [Turn over (c) (i) A major use of sodium metal is in street lamps. The lamp contains mercury vapour which conducts electricity at high voltages. Sodium within the lamp vaporises and the electrical energy causes yellow (orange) light to be given out. When the light from the sodium lamp is analysed, the spectrum shows two bright yellow lines at wavelengths of 589 nm and 589.6 nm. (1 nm = 1 10 9 m) 589 Examiner Only Marks Remark 589.6 Using the equations E = hv and c = v , calculate the energy change (in joules) associated with the line at 589 nm. (c = 3 108 m s 1). _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (ii) Explain how you could carry out a flame test and a test for chloride ions to identify a white solid as sodium chloride. Write equations for any reactions taking place. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [5] 4975 12 [Turn over (d) If larger amounts of energy are supplied to sodium vapour (gas) it ionises. Examiner Only Marks Remark (i) Write the equation which represents the first ionisation energy of sodium including state symbols. ___________________________________________________ [2] (ii) The value of the first ionisation energy for sodium is 500 kJ mol 1. The second ionisation energy has a value of 4513 kJ mol 1. Explain why this is a much higher value. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (e) Using diagrams, explain why sodium is able to conduct electricity whether solid or molten, while sodium chloride conducts only when molten or dissolved in water. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [5] Quality of written communication 4975 [2] 13 [Turn over 17 In the laboratory, ammonia can be prepared by heating a mixture of ammonium chloride and calcium hydroxide as shown in the diagram below. Examiner Only Marks Remark ammonia ammonium chloride + calcium hydroxide heat The equation for the reaction is: 2NH4Cl + Ca(OH)2 2NH3 + CaCl2 + 2H2O (a) The ammonia gas is collected upwards. Calculate the relative molecular masses of ammonia, NH3, oxygen, O2 and nitrogen, N2, and use them to explain why ammonia is collected in this way. ammonia ___________________________________ oxygen _____________________________________ nitrogen _____________________________________ explanation _______________________________________________ _______________________________________________________ [2] (b) Calculate the volume of ammonia produced, at 20 C and one atmosphere pressure, if 1.07 g of ammonium chloride are heated with excess calcium hydroxide. _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] 4975 14 [Turn over (c) Ammonia gas is alkaline. Examiner Only Marks (i) Describe the effect of ammonia on moist Universal Indicator paper. ___________________________________________________ [1] (ii) Ammonia may be detected using concentrated hydrochloric acid. Write the equation for the reaction and describe what is observed. _____________________________________________________ ___________________________________________________ [2] (d) Ammonia can act as a reducing agent. When passed over heated copper(II) oxide, the following reaction occurs: 2NH3 + 3CuO 3Cu + N2 + 3H2O Deduce the oxidation numbers of nitrogen and copper in the reactants and products and use them to explain the redox change. _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] THIS IS THE END OF THE QUESTION PAPER 4975 15 Remark 938-047-1

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Additional Info : Gce Chemistry June 2009 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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