IJC H1 CHEM P2 QP

INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2 in preparation for General Certificate of Education Advanced Level Higher 1 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Structured and Free Response Questions Section A: Structured Candidates answer Section A on the Question Paper Section B: Free Response Additional Materials: Writing Paper Data Booklet 8872/02 2 Sept 2015 2 hours READ THESE INSTRUCTIONS FIRST Write your index number, name and civics group on all the work you hand in. Write in dark blue or black pen. You may use pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A: Structured Questions (40m) Answer all questions in the space provided. Section B: Free Response Questions (40m) Answer two questions on separate writing papers. You are advised to show all working in calculations. You are reminded of the need for good English and clear presentation in your answers. You are reminded of the need for good handwriting. Your final answers should be in 3 significant figures. You may use a calculator. 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. This document consists of 13 printed pages and 1 blank page. Innova Junior College [Turn over For Examiner’s Use Section A 1 12 2 8 3 10 4 10 Section B 20 20 Significant figures Handwriting Total 80

2  IJC 2015 Prelim 2/8872/02 [Turn over For Examiner’s Use Section A Answer ALL questions on the spaces provided. 1 Chromium is a transition metal. Chromium compounds are highly valued as pigments for their vivid green, yellow, red and orange colours. (a) The element chromium has four main naturally occurring isotopes. isotope relative abundance / % 50Cr 4.33 52Cr 83.8 53Cr 9.50 54Cr 2.37 Use the relative abundance data to calculate the relative atomic mass of Cr, showing your working clearly. [1] (b) Chromium(III) chloride dissolves in water to form a green solution. Draw a labelled diagram to illustrate the interaction between a Cr 3+ ion and a water molecule. [2] (c) Chromium(IV) oxide, CrO 2 is a black solid that disproportionates into a mixture of Cr3+ and Cr2O7 2– in acidic solutions. The half-equation for the reduction of CrO 2 to Cr3+ is as follows: CrO2 + 4H+ + e Cr3+ + 2H2O To determine the percentage purity of a sample of chromium( IV) oxide, a student dissolves 1.5 g of impure sample in 20 cm 3 of sulfuric acid and make up the total volume to 100 cm 3 with distilled water. He then found that 25 cm 3 of the resulting solution, containing Cr 2O7 2– ions, required 16.00 cm 3 of 0.200 mol dm -3 of iron( II) sulfate solution for complete reaction. (i) Construct the half-equation for the oxidation of CrO2 to Cr2O7 2–. …………………………………………………………………………………………

3  IJC 2015 Prelim 2/8872/02 [Turn over For Examiner’s Use (ii) Hence, construct the overall equation for the disproportionation of CrO 2 to Cr3+ and Cr2O7 2–. ........................................................................................................................... ………………………………………………………………………………………… ………………………………………………………………………………………… (iii) Calculate the amount of Fe 2+ used in the reaction. (iv) Hence, calculate the amount of Cr 2O7 2– present in 100 cm3 of the solution. (v) Calculate the mass of CrO 2 present in the sample and hence, the percentage purity of the sample. [You may assume a mole ratio of CrO 2 : Cr2O7 2– of 6 : 1 if you were unable to derive the overall equation in (ii).] [7] (d) Beams of charged particles are deflected by an electric field. lf the particles are all travelling at the same speed, through an electric field of constant strength, the angle of deflection is proportional to their charge/mass ratio. ln a particular experimental set-up, protons are deflected through an angle of +15 o. (i) Assuming an identical set of experimental conditions, by what angle will Cr 3+ be deflected?

4  IJC 2015 Prelim 2/8872/02 [Turn over For Examiner’s Use (ii) Under identical conditions, a beam of particles, A, each having 12 times the mass of a proton, was deflected by an angle of +5o. Suggest the overall charge on a particle of A. [2] [Total: 12] 2 (a) The table below shows the lattice energies for the sodium halides and magnesium oxide. compound lattice energy / kJ mol 1 NaCl 781  NaBr 743  NaI 699  MgO 3933  (i) Define the term lattice energy. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… (ii) By quoting appropriate data from the Data Booklet , explain why the lattice energy of MgO is considerably larger than those of the sodium halides. ………………………………………………………………………………………… ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… [4]

5  IJC 2015 Prelim 2/8872/02 [Turn over For Examiner’s Use (b) The 1,2-dichloroethene molecule can exist in either of the following forms, B or C as shown: By considering the polarity of the molecule, predict which form, B or C, has a lower boiling point. Explain your answer. ……………………………………………………………………………………………….. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. [2] (c) Account for the following observation: At around 30 oC, the relative molecular mass of hydrogen fluoride appears to be 40.0 and above 60 oC, it is about 20.0. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………….…… [2] [Total: 8] 3 (a) Using blood as an example, explain what is meant by an acidic buffer solution. …………………………………………………………………………………………….... …………………………………………………………………………………………….... ………………………………………………………………………………………………. ..…………………………………………………………………………………………….. …..………………………………………………………………………………………….. ……..……………………………………………………………………………………….. ………..…………………………………………………………………………………….. …………...…………………………………………………………………………………. [5]

6  IJC 2015 Prelim 2/8872/02 [Turn over For Examiner’s Use (b) Benzene is used as the starting reagent for the production of many aromatic compounds shown below. Long-term exposure to high levels of benzene in the air can cause leukaemia, cancer of the blood-forming organs. (i) Draw the structure of E in the space given above. (ii) State the reagents and conditions needed to convert D to F. ……………………………………………… ……………………………………...… (iii) F can react with a suitable re