YJC H1 Chem P2

YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE CANDIDATE’S NAME: ______________________ CTG: _________ YISHUN JUNIOR COLLEGE PRELIMINARY EXAMINATION CHEMISTRY 8872/02 Higher 1 2 hours Paper 2 Additional materials: Answer Paper Data Booklet INSTRUCTIONS TO CANDIDATES Write your name and CTG in the spaces at the Answer all questions. Write your answers in the writing papers provided. For numerical answers, all working should be shown clearly. At the end of the paper, fasten all your answer to. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at For Examiner’s Use Section A 1 /14 2 /7 3 /8 4 /11 Sub-total /40 Section B Sub-total /40 Total /80 This question paper consists of 14 printed pages READ THESE INSTRUCTIONS FIRST Write your Name and CTG on cover page. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for diagrams, graphs or rough working. Do not use staples, paper clips, hightlighters, glue or correction fluid. Section A Answer all questions. Section B Answer two questions on separate answer paper. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

8872/YJC/P2/2009 2 Section A Answer all the questions in this section in the spaces provided. 1 Sir James Jeans, who was a great populariser of science, once described an atom of carbon as being like six bees buzzing round a space the size of a football stadium. (a) (i) Suggest what were represented by the six bees in this description. (ii) Explain (in terms of an atom of carbon) what stopped the bees from flying away from the space of the football stadium. (iii) What is missing from Jeans’ description when applied to an atom of carbon? [3] (b) A sample of oxygen consisting mainly of the isotope oxygen-16 was enriched with oxygen-18. The oxygen sample reacted with sodium as follows: 4Na (s) + O2 (g) → 2Na2O (s) (i) Complete the table below to show the composition of some of the species involved in the reaction species protons neutrons electrons

8872/YJC/P2/2009 3 (ii) Write an equation for sodium oxide reacting with nitric acid. (iii) The relative atomic mass of the oxygen sample is 16.5. Calculate the relative abundance of the two oxygen isotopes. [5] (c) Nitrogen and oxygen are found in the second period of the Period Table. (i) Complete the electron configurations of nitrogen and oxygen on the energy level diagrams below, using arrows to represent electrons. energy nitrogen oxygen 1s 1s

8872/YJC/P2/2009 4 (ii) Explain, with reference to your answer to (c)(i), the relative values of the first ionisation energies of nitrogen and oxygen. The values are given in the Data Booklet and should be quoted in your answer. (iii) State the formula of the negatively charged ion formed by nitrogen in simple binary compounds. (iv) Why do nitrogen and oxygen form negative ions but not positive ions, in simple binary compounds? [6] [Total: 14] 2 This question is about hydrogen peroxide, H2O2, and its decomposition. (a) (i) Draw a “dot and cross” diagram to show the electronic structure for hydrogen peroxide, showing outer electrons only.

8872/YJC/P2/2009 5 (ii) State the shape and O−O−H bond angle. [2] (b) Hydrogen peroxide is a liquid at room temperature. With an aid of a diagram, identify and show the intermolecular force between hydrogen peroxide molecules. [1] (c) Hydrogen peroxide decomposes slowly at room temperature. 2H2O2 (aq) → O2 (g) + 2H2O (l) Explain, using oxidation numbers, why this is a disproportionation reaction. [1] (d) The oxidation number of vanadium in a complex ion was determined as follows. 2.08 x 10-3 mol sample of the complex was dissolved in water and the solution made up to 100 cm3. A 25.0 cm3 portion of this solution required 5.20 x 10-4 mol of H2O2 to oxidise all the vanadium to the +5 oxidation state. Given the reaction H2O2 undergoes is H2O2 + 2H+ + 2e-  2H2O, calculate

8872/YJC/P2/2009 6 (i) the number of moles of vanadium complex in 25.0 cm3 portion. (ii) the original oxidation number of the vanadium in the complex. [3] [Total: 7] 3 (a) (i) In the boxes below, write the formulae of one of the chlorides of each of these four elements and the pH of its aqueous solutions. sodium magnesium aluminium phosphorus formula pH (ii) Write an equation to justify the pH you have written in (a)(i) for the aqueous solution of the chloride of phosphorus.

8872/YJC/P2/2009 7 (b) The lattice energy of sodium chloride is 769 kJ mol-1. How you would expect the lattice energy of magnesium oxide to differ from that of sodium chloride? Explain your answer. [5] (c) Aluminium fluoride and aluminium chloride each sublimes when heated. The former has a sublimation point of 1270oC whereas the latter’s sublimation point is 178oC. (i) Use these data to suggest the nature of the bonding in both aluminium halides, explaining your answer. (ii) Aluminium chloride can react with ammonia in a molar ratio of 1:1 to form a product X. Give the full structural formula for X, showing clearly the type of bonds present. [3] [Total: 8]

8872/YJC/P2/2009 8 4 A student obtained the following results when analysing an organic compound, A. test observation test 1 relative molecular mass 86 test 2 % composition by mass C, 69.8%; H, 11.6%; O, 18.6% test 3 reactions with Br2 in CCl4 Br2 decolourised test 4 reaction with Na H2 (g) evolved test 5 reaction with warm alkaline