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GCE JAN 2008 : (AS 1) General Chemistry

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education January 2008 Chemistry assessing Module 1: General Chemistry ASC11 Assessment Unit AS 1 [ASC11] THURSDAY 17 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. 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 13(a)(iii). 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. ASC1W8 3429 11 12 13 14 15 16 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 Which one of the following solids consists of molecular covalent crystals? A B C D 2 Which one of the following compounds does not exhibit hydrogen bonding? A B C D 3 Diamond Graphite Quartz Rhombic sulphur Ammonia, NH3 Ethanol, C2H5OH Methane, CH4 Water, H2O Which one of the following graphs represents the change in melting point across the third period from sodium to argon? A B melting point melting point atomic number atomic number C D melting point melting point atomic number ASC1W8 3429 atomic number 2 [Turn over 4 The hydrogen spectrum is best described as a series of A B C D 5 equally spaced lines. lines becoming closer together as the frequency increases. lines becoming closer together as the wavelength increases. lines becoming closer together and then further apart. Magnesium has three isotopes as shown below. Relative atomic mass 24 25 26 A B C D 6 78.6 10.1 11.3 24.00 24.08 24.32 24.33 In an experiment 3.425 g of lead oxide were reduced to form 3.105 g of lead. What is the empirical formula of the lead oxide? A B C D 7 Percentage abundance (%) PbO Pb3O2 Pb3O4 Pb4O3 Which one of the following ions has the smallest radius? A B C D ASC1W8 F Mg2+ Na+ O2 3429 3 [Turn over 8 The electronegativity values for carbon, fluorine, nitrogen and oxygen are given below. Which one of these values is most likely to be that of nitrogen? A B C D 9 2.5 3.0 3.5 4.0 Which one of the following is responsible for the open structure of ice? A B C D Covalent bonds Dipole dipole attractions Hydrogen bonds Van der Waals forces 10 Phenol is converted to trichlorophenol (TCP) according to the equation below. C6H5OH + 3Cl2 C6H2Cl3OH + 3HCl If 50.0 g of phenol produced 97.6 g of TCP, what is the percentage yield of the TCP? A B C D ASC1W8 47.6% 49.4% 51.2% 92.9% 3429 4 [Turn over Section B Examiner Only Marks Remark Answer all six questions in this section. 11 Metal salts are used to produce colours in fireworks. (a) Complete the table below to give the flame colour of each of the metal chlorides listed. Metal chloride Flame colour Barium chloride Strontium chloride [2] (b) Using a diagram, explain how the flame colours of the metal chlorides originate. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________________ [3] ASC1W8 3429 5 [Turn over 12 Beryllium chloride, BeCl2, and ammonia, NH3, are covalent compounds. Examiner Only Marks Remark (a) State the octet rule and explain whether beryllium chloride obeys the rule. _________________________________________________________ _________________________________________________________ ______________________________________________________________ [2] (b) The ammonium ion, NH4+, contains a coordinate bond. (i) Explain what is meant by a coordinate bond. ________________________________________________________ _____________________________________________________ [1] (ii) Draw a dot and cross diagram, using outer electrons only, to show the bonding in an ammonium ion. [2] ASC1W8 3429 6 [Turn over 13 A dilute solution of hydrogen peroxide can be used as an antiseptic mouthwash. Examiner Only Marks Remark The concentration of the hydrogen peroxide solution can be measured by reaction with excess acidified potassium iodide solution. H2O2 + 2H+ + 2I 2H2O + I2 The liberated iodine is then estimated by titration with standard sodium thiosulphate solution. (a) (i) Name the indicator used in this titration. _____________________________________________________ [1] (ii) Explain what is meant by the term standard solution. ________________________________________________________ _____________________________________________________ [1] (iii) Describe, giving experimental detail, how you would carry out the titration. Assume all the apparatus is clean and dry. ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ _____________________________________________________ [4] Quality of written communication ASC1W8 3429 [2] 7 [Turn over (b) 25.0 cm3 of the mouthwash was diluted to 250 cm3. A 25.0 cm3 portion of the diluted mouthwash required 22.5 cm3 of 0.1 M sodium thiosulphate for a complete reaction. Examiner Only Marks Remark (i) Write an equation for the reaction between sodium thiosulphate, Na2S2O3, and iodine I2. __________________________________________________ [2] (ii) Calculate the concentration of the hydrogen peroxide in the mouthwash in g dm 3 using the following headings: Number of moles of sodium thiosulphate used. ________________________________________________________ Number of moles of iodine, I2, liberated in 25.0 cm3 of diluted mouthwash solution. ________________________________________________________ Number of moles of H2O2 present in 25.0 cm3 of diluted mouthwash solution. ________________________________________________________ Number of moles of H2O2 in 25.0 cm3 of undiluted mouthwash. ________________________________________________________ Mass of H2O2 in 25.0 cm3 of undiluted mouthwash. ________________________________________________________ Concentration of H2O2 in undiluted mouthwash in g dm 3. _____________________________________________________ [4] ASC1W8 3429 8 [Turn over 14 Kerosene is a mixture of hydrocarbons. When it is mixed with hydrogen peroxide it can be used as a rocket fuel. Examiner Only Marks Remark (a) The kerosene burns in oxygen released by the hydrogen peroxide. (i) One component of kerosene is dodecane, C12H26. Write an equation for the complete combustion of dodecane. _____________________________________________________ [2] (ii) Draw an enthalpy level diagram for the combustion of dodecane using the axes below, labelling the y-axis. [2] Extent of reaction (iii) Explain, in terms of enthalpy, why the combustion of dodecane is exothermic. ________________________________________________________ ________________________________________________________ _____________________________________________________ [2] ASC1W8 3429 9 [Turn over (b) The enthalpy of combustion of hydrocarbons can be calculated using Hess s Law. Examiner Only Marks Remark (i) Explain what is meant by the term standard enthalpy of combustion. ________________________________________________________ ________________________________________________________ _____________________________________________________ [2] (ii) State Hess s Law. ________________________________________________________ ________________________________________________________ _____________________________________________________ [2] (iii) One of the constituents of petrol is octane, C8H18. Use the information below to calculate the enthalpy of combustion of octane. 1 C8H18(l) + 12 O2(g) 8CO2(g) + 9H2O(l) 2 C(s) + O2(g) CO2(g) 8C(s) + 9H2(g) C8H18(l) 1 H2(g) + O2(g) H2O(l) 2 H = 393.5 kJ mol 1 H = 250.0 kJ mol 1 H = 286.0 kJ mol 1 ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ Enthalpy of combustion ___________________ kJ mol 1 [3] ASC1W8 3429 10 [Turn over (c) The enthalpy of combustion can also be calculated using bond enthalpy values. Examiner Only Marks Remark (i) Explain what is meant by the term bond enthalpy. ________________________________________________________ _____________________________________________________ [1] (ii) Use the bond enthalpy values below to calculate the total bond enthalpy for the products and the overall enthalpy change for the combustion of 1 mole of octane given that the total of the bond enthalpies of the reactants is 16 548 kJ. Bond Bond enthalpy C=O H O 750 kJ mol 1 463 kJ mol 1 ________________________________________________________ ________________________________________________________ Total bond enthalpy of products _______________ Enthalpy change for the combustion of octane ________________ [2] (iii) Explain the difference in the value of the enthalpy of combustion from Hess s Law with that obtained using bond enthalpies. ________________________________________________________ ________________________________________________________ _____________________________________________________ [2] ASC1W8 3429 11 [Turn over 15 Sodium and fluorine are reactive elements which combine directly to form the ionic salt, sodium fluoride. Examiner Only Marks Remark (a) Sodium has the typical properties of a metal. (i) Draw a diagram to show the bonding in sodium metal. [2] (ii) Explain why sodium is malleable. ________________________________________________________ _____________________________________________________ [1] conducts electricity. ________________________________________________________ _____________________________________________________ [2] (b) (i) Write an equation, including state symbols, for the formation of sodium fluoride from sodium and fluorine. _____________________________________________________ [2] (ii) Draw dot and cross diagrams, using outer electrons only, to show the formation of sodium fluoride from sodium and fluorine atoms. [3] ASC1W8 3429 12 [Turn over (iii) Suggest why fluoride is added to some toothpastes. Examiner Only Marks Remark _____________________________________________________ [1] (iv) Explain why some people object to the fluoridation of drinking water. ________________________________________________________ _____________________________________________________ [1] (c) The graph below represents the first ionisation energies of elements from sodium to argon. first ionisation energy 15 16 12 13 atomic number (i) Explain the general rise in the first ionisation energy across the period. ________________________________________________________ ________________________________________________________ _____________________________________________________ [2] (ii) Explain the decrease in the first ionisation energy from numbers 12 to 13 and from 15 to 16. 12 to 13 ________________________________________________ ________________________________________________________ 15 to 16 ________________________________________________ _____________________________________________________ [2] ASC1W8 3429 13 [Turn over (iii) Complete the graph of the successive ionisation energies of sodium. Examiner Only Marks Remark log ionisation energy 1 2 3456789 number of electron removed 10 11 [2] ASC1W8 3429 14 [Turn over 16 The halogens fluorine, chlorine, bromine, iodine and astatine form Group VII of the Periodic Table. Examiner Only Marks Remark (a) Fluorine is the most electronegative element. Explain what is meant by the term electronegative element. ___________________________________________________________ ________________________________________________________ [1] (b) The halogens react with hydrogen to form hydrogen halides. (i) Write an equation for the reaction between fluorine and hydrogen. _____________________________________________________ [1] (ii) Show the polarity of the hydrogen fluorine bond on the diagram below. H F [1] (iii) State and explain the trend in the thermal stability of the hydrogen halides. ________________________________________________________ ________________________________________________________ _____________________________________________________ [2] (iv) The hydrogen halides dissolve in water to form acidic solutions. List the hydrogen halides in order of increasing acidic strength. Weakest acid: ______________________ ______________________ ______________________ ______________________ Strongest acid: ASC1W8 3429 ______________________ 15 [1] [Turn over (c) The sodium salts of these acids are colourless ionic solids. Examiner Only Marks Remark (i) How could you distinguish between solid samples of sodium chloride and sodium bromide using aqueous silver nitrate and dilute ammonia solution? ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ _____________________________________________________ [4] (ii) Write the equation for the reaction of sodium bromide with concentrated sulphuric acid. _____________________________________________________ [2] (iii) Give two observations when concentrated sulphuric acid is added to solid sodium iodide. ________________________________________________________ ________________________________________________________ _____________________________________________________ [2] ASC1W8 3429 16 [Turn over (d) Chlorine reacts with cold dilute sodium hydroxide according to the equation: Examiner Only Marks Cl2 + 2NaOH NaCl + NaOCl + H2O (i) State the oxidation number of chlorine in each of the following species. Cl2 _________________ NaCl _________________ NaOCl _________________ [3] (ii) Explain, using the oxidation numbers, why this is described as a redox reaction. ________________________________________________________ _____________________________________________________ [2] (iii) What name is given to this type of redox reaction? _____________________________________________________ [1] THIS IS THE END OF THE QUESTION PAPER ASC1W8 3429 17 Remark S 2/07 302-023-1

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Additional Info : Gce Chemistry January 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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