RVHS H2 Chem 2012 Prelim P2 QP

CANDIDATE NAME CLASS CENTRE NUMBER RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION 6 S INDEX NUMBER H2 CHEMISTRY 9647/02 Paper 2 Structured Questions 11 September 2012 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class, Centre number and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the space provided. A Data Booklet is provided. Do NOT write anything on it. 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. For Examiner’s Use Paper 2 Question 1 2 3 4 5 6 7 8 TotalNumber Marks 12 7 7 6 10 9 13 8 72 Paper 1 40 Paper 3 80 Total 192 ____________________________________________________________________________ This document consists of 17 printed pages and 1 blank page. River Valley High School 9647/02/PRELIM/12 [Turn over Preliminary Examination 2012

River Valley High School 9647/02/PRELIM/12 [Turn over Preliminary Examination 2012 2 1 Planning (P) Calcium salts are used in many industrial processes. Calcium oxide is used in the production of cement while calcium nitrate is sometimes used to accelerate the setting of concrete. Calcium oxide is a white hygroscopic solid. Calcium oxide can react with water and as such can cause severe irritation when in contact with skin, eyes or if inhaled. Calcium nitrate is a lso a white hygroscopic solid. Calcium nitrate decomposes on heating to form the oxide, nitrogen dioxide and oxygen. (a) Write a balanced equation, including state symbols, for the thermal decomposition of calcium nitrate. …………………………………………………………………........ ............. [1] (b) Calculate the change in mass of the solid you would expect if 1.00 mol of calcium nitrate underwent thermal decomposition. [1] (c) A container of calcium nitrate was contaminated with calcium oxide. Design an experiment to determine the percentage purity of calcium nitrate by a gravimetric method. You are provided with about 2 g of the impure calcium nitrate. (In gravimetric methods, the object ive is to fo rm a thermally stable solid so that the mass can be determined accurately for analysis.) Your plan should include the following: · A full description of the procedure. · Details of how you would calculate the percentage purity from the measurements made. [Mr of Ca(NO3)2 = 164] …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ ..............

River Valley High School 9647/02/PRELIM/12 [Turn over Preliminary Examination 2012 3 …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. [8] (d) State and explain clearly one precaution you would take to improve the accuracy of your results. …………………………………………………………………........ .............. …………………………………………………………………........ .............. …………………………………………………………………........ .............. [1] (e) Identify one potential safety hazard in this experiment and state how you would minimise the risk. …………………………………………………………………........ .............. …………………………………………………………………........ .............. [1] [Total: 12]

River Valley High School 9647/02/PRELIM/12 [Turn over Preliminary Examination 2012 4 2 Titanium(IV) oxide, TiO2, is the naturally occurring oxide of titanium. It is the main ingredient in sunscreen lotion due to its high refractive index and strong UV-light absorbing capability. (a) Using the following information as well as relevant data from the Data Booklet, draw a Born- Haber cycle for the formation of TiO 2(s) and calculate the lattice energy of TiO2(s). Standard enthalpy change of formation of TiO2(s) −945 kJ mol−1 Standard enthalpy change of atomisation of Ti +471 kJ mol−1 1st electron affinity of oxygen −142 kJ mol−1 2nd electron affinity of oxygen +844 kJ mol−1 [3]

River Valley High School 9647/02/PRELIM/12 [Turn over Preliminary Examination 2012 5 (b) Crude titanium( IV) oxide is purified via the Chloride process. In this two-step process, the crude ore (containing at least 70% titanium( IV) oxide) is first reacted with carbon and chlorine, represented by the equation shown below. TiO2(s) + C(s) + 2Cl2(g) ® TiCl4(l) + CO2(g) Standard enthalpy change of formation of TiCl4(l) −804 kJ mol−1 Standard enthalpy change of formation of CO2(g) −394 kJ mol−1 Standard molar entropy of TiO2(s) +49.9 J mol−1 K−1 Standard molar entropy of C(s) +5.7 J mol−1 K−1 Standard molar entropy of Cl2(g) +223 J mol−1 K−1 Standard molar entropy of TiCl4(l) +252 J mol−1 K−1 Standard molar entropy of CO2(g) +214 J mol−1 K−1 Using the above information, as well as relevant data from (a) and the Data Booklet, calculate, for the first step of the Chloride process, (i) the standard enthalpy change of reaction, (i i) the standard entropy change of reaction. Note: DS , = SS,(products) – SS,(reactants) [2]

River Valley High School 9647/02/PRELIM/12 [Turn over Preliminary Examination 2012 6 (c) Using your answers in (b) , determine if the first step of the Chloride process is spontaneous at 2000 K. [1] (d) The second step of the Chloride process involves the titanium (IV) chloride being distilled off and oxidised in a pure oxygen flame to give pure titanium(IV) oxide and chlorine gas. Write an equation for the reaction in the second step. …………………………………………………………………........ ............. [1] [Total: 7] 3 Neidong Forest Recreation National Park, located in the Wulai District in Taipei, has the highest concentration of anions in Taiwan due to the numerous waterfalls and lush forestation in the park. Anions are said to help boost the immune system, among other health benefits. (a) Bromide ions are thought to be one of the anions present in abundance. The concentration of bromide ions in the river waters can be used as an estimate of the concentration of the ions in the park. A 25.0 cm 3 sample of river water was collected and 50.0 cm 3 of 1.00 mol dm –3 Pb(NO3)2 was added. The precipitate formed was filtered off and 3.00 g of precipitate was collected. The filtrate can be regarded as a saturated solution of PbBr2. (i) Calculate the concentration of Pb2+ ions in the filtrate.

River Valley High School 9647/02/PRELIM/12 [Turn over Preliminary Examination 2012 7 (i i) Write an expression for the solubility product, Ksp, of PbBr2. …………………………………………………………………........ .... (iii) The numerical value for the Ksp of PbBr2 is 3.9 ´ 10–5. Determine the concentration of bromide ions in the s