CJC Prelim H2 Chem 2008 P2

Name Class CATHOLIC JUNIOR COLLEGE PRELIMINARY EXAM 2008 CHEMISTRY 9746/02 CHEMISTRY 9746/02 Higher 2 Higher 2 Paper 2 Structured Questions 26 August 2008 Paper 2 Structured Questions 26 August 2008 Candidates answer on the Question Paper. 1 hour 30 mins Candidates answer on the Question Paper. 1 hour 30 mins Additional Materials: Data Booklet Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST READ THESE INSTRUCTIONS FIRST Write your name and class in the spaces at the top of this page. Write your name and class in the spaces at the top of this page. Write in dark blue or black pen. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. You may use a soft pencil for any diagrams, graphs or rough working. Do not use correction fluid. Do not use correction fluid. Answer all questions. Answer all questions. You are advised to show all working in calculations. You may use a calculator. You are advised to show all working in calculations. You may use a calculator. A Data Booklet is provided. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part The number of marks is given in brackets [ ] at the end of each question or part question. question. For Examiner’s Use 1 2 3 4 5 6 Total 60 This document consists of 9This document consists of 9 printed pages and 1 blank page.

2 1 Explain the following observations: (a) Sulphur has a lower first ionisation energy than phosphorus. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [2] (b) Carbon dioxide and silicon dioxide have widel y different melting points. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [2] (c) 2-Nitrophenol has a lower me lting point than 4-nitrophenol. [2] (d) The boiling points of hydrogen ha lides are of the following order. Compound HF HCl HBr HI Boiling point/ °C 19.4 -85.1 -66.4 -35.6 …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [2] (e) The bond angle in PCl 3 is larger than that in AsCl3. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [2] [Total: 10] CJC 2008 9746/02/prelim/08

3 Use of the Data Booklet is relevant to this question. 2 A 1.00 g sample of steel was dissolved in excess nitric acid. The resulting solution was found to contain manganese(II) ions. On addition of sodium bismuthate, NaBiO3, all the manganese(II) ions were oxidised to manganate(VII) ions. After removing any excess bismut hate ions, the resulting purple solution was titrated with a solution containing iron(II) ions of concentration 0.10 mol dm-3. 36.00 cm 3 of this solution was required to reach the endpoint, in which iron(II) ions were oxidised to iron(III) ions. (a) What is the oxidation state of bismuth in NaBiO3? ………………………………………………………………..…………………………[1] (b) (i) Given that the bism uthate ion is reduced to Bi 3+, write the half-equation for this reduction reaction. ………………………………………………………………..…………………………… (ii) Hence, write an overall bal anced equation for the oxidation of manganese(II) to manganate(VII) by bismuthate ions in acidic solution. ………………………………………………………………..…………………………… [ 2 ] (c) Calculate the percentage by mass of manganese in the steel sample. [3] (d) (i) Calculate the E θ cell for each of the following reactions in the table below and hence deduce whether each reaction can occur under standard conditions. Reactants Products Eθ cell / V Can reaction occur? (Y/N) Mn & SO4 2- Mn 2+ & SO2 Mn2+ & SO4 2- MnO 4 - & SO2 Fe2+ & SO4 2- Fe 3+ & SO2 (ii) Using your answers from (d)(i), state and explain whether sulphuric acid is a suitable replacement for nitric acid in this experiment. [4] [Total: 10] CJC 2008 9746/02/prelim/08

4 3 (a) Paracetamol is a common analgesic drug oft en used as a painkiller and for treating mild fever. In a study carried out to determine the rate of removal of paracetamol from the body, the reaction was found to have a constant half-life of 2.7 h. (i) Sketch a graph to show how the concentration of paracetamol changes with time. [paracetamol ] time / h (ii) A boy took a dose of paracetamol (two 500 mg tablet) for his fever. How long does it take for the paracetamol in his body to decrease to 125 mg? (iii) An independent study s hows that the removal of paracetamol from the body could be accelerated by using enzymes. On the same axes in (a)(i), sketch and label clearly the graph expected for the enzyme-catalysed reaction. (iv) The enzyme-catalyst only works well under certain conditions in the body. Suggest one condition which would affect the action of the enzyme-catalyst. …..………………………….……………….……………………..………………... [5] CJC 2008 9746/02/prelim/08

5 (b) The following reaction sc heme involved a halogeno compound V. CH2CH3 Cl CH=CH2 Cl step I V HCl (i) Draw the structural formula of V. (ii) Suggest reagents and c onditions required for step I. (iii) Draw diagrams to illustrate the type of stereoisomerism exhibited by V. (iv) When V is boiled under reflux with excess ethanolic silver nitrate, a white precipitate is formed. What is the mass of the precipitate formed if 1.75 g of V is used in the reaction? [5] [Total: 10] CJC 2008 9746/02/prelim/08

6 4 (a) A hydrocarbon W contains 92.3 % carbon. On complete combustion, 0.005 mol of W produced 1.76 g of CO2. (i) Determine the molecular formula of W . (ii) Given that W forms a white precipitate on heating with acidified potassium manganate(VII) and 1 mol of W reacts with 1 mol of bromine gas in tetrachloromethane, draw the displayed formula of W. (iii) State the type of hybridisat ion shown by the carbon atoms of W and draw the hybrid orbitals. W forms a monochlorinated product X that is able to exhibit stereoisomerism. (iv) State the type of st ereoisomerism shown by X. (v) Draw and clearly label the two stereoisomers of X. [ 8 ] (b) Nickel metal, used in the reaction described in (a)(ii), is a transition metal. Explain the data given below. Atomic Size/nm Melting Point / oC Ni 0.115 1453 Ca 0.197 842 [2] [Total: 10] CJC 2008 9746/02/prelim/08

7 5 At 375 K, the equilibrium constant Kp for the following reaction shown below is 2.4 atm. S O 2Cl2 (g) SO2 (g) + Cl2 (g) (a) 6.7 g of gaseous SO 2Cl2 was placed into a 1 dm 3 vessel and the temperature was held constant at 375 K. What is the initial pressure of SO 2Cl2 (in atm) in the vessel before dissociation? (1 atm = 1.01 x 105 Pa) [ 1 ] (b) Using your answer in (a), write a K p expression in terms of the partial pressure of SO2, pSO2, only. Hence, determine the partial pressures of SO 2, Cl2, and SO2Cl2 at equilibrium. [ 3 ] (c) If 1.0 atm of Cl 2 was initially present al ong with the 6.7 g of SO 2Cl2, give the partial pressure terms of Cl 2 and SO2Cl2 in terms of the par tial pressure of SO 2, pSO2, only and hence determine the corresponding equilibrium partial pressures of the gases.