DHS H2 Chem 2012 Prelim P1 QP

Name: Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination Year 6 H2 CHEMISTRY 9647/01 Paper 1 Multiple Choice 20 September 2012 1 hour Additional Materials: Optical Answer Sheet Data Booklet INSTRUCTIONS TO CANDIDATES 1. Write your name, index number and class on this question paper. 2. There are forty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Optical Mark Sheet. 3. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. 4. Any rough working should be done in this booklet. 5. You may use a calculator. This question paper consists of 21 printed pages and 1 blank page.  DHS 2012 [Turn over

2 Ó DHS 2012 9647/01 [Turn over Section A For each question there are four possible answers, A , B, C and D. Choose the one you consider to be correct. 1 To determine the mass of arsenic present in a sample of pesticide, all the arsenic was first converted to arsenate ion, AsO 43-. 1.25 x 10 -3 mol of AgNO3 was then added to precipitate AsO 43- as Ag 3AsO4. The excess Ag + ions needed 3.64 cm 3 of 0.054 mol dm-3 KSCN to form silver thiocynate, AgSCN. Calculate the mass of arsenic (Ar = 74.9) present in the sample of pesticide. A 0.015 g B 0.026 g C 0.079 g D 0.488 g 2 In an experiment, a sample was vapourised, ionised and passed through an electric field. Analysis of the deflection occurring at the electric region revealed the following data for the sample. It was observed that a beam of Na + gives an angle of deflection of 4.3°. What are the possible identities of unknown particles, q and r, and the value of a? q r a A Be2+ Br- 22.0° B Be2+ S2- 6.2° C Ba2+ Br- 1.2° D Ba2+ S2- 1.4° + »4.4a

3 Ó DHS 2012 9647/01 [Turn over 3 How many moles of electrons must be removed from each mole of methylbenzene, C6H5CH3, when it is oxidised to benzoic acid, C6H5COOH? A 1 B 2 C 4 D 6 4 Which graph correctly describes the behaviour of fixed masses of the ideal gases I and J, where I has a higher Mr than J? A B C D T PV Constant P I J T PV Constant P J I Constant T J I PV P Constant T I J PV P

4 Ó DHS 2012 9647/01 [Turn over 5 A student used the set–up below to heat a can containing 300 g of water. The following data were recorded: mass of propan–1–ol burnt = m g change in temperature of water = DT °C Given that: relative molecular mass of propan–1–ol = 60.0 enthalpy change of combustion of propan–1–ol = –2021 kJ mol–1 specific heat capacity of water = c J g–1 K–1 What is the efficiency of this heating process? A %. T c m 100060300 10002021 ´´ D ´ ´ ´ ´ B %. T c m10010002021 300 060 ´´ ´ ´ D ´ ´ C %m . T c1002021 060300 ´´ ´ D ´ ´ D %m . T c10010002021 060300 ´´ ´ ´ D ´ ´ 6 Which of the following statements best explains why calcium and chlorine form CaC l2 rather than CaCl? A Less energy is required to remove one electron from the calcium atom than to remove two electrons. B More energy is released in forming chloride ions from chlorine molecules in the formation of CaCl2(s) than in the formation of CaCl(s). C The lattice energy of CaCl(s) is less exothermic than that of CaCl2(s). D When CaCl(s) is formed from its elements, more energy is released than when CaCl2(s) is formed from its elements.

5 Ó DHS 2012 9647/01 [Turn over 7 An exothermic chemical reaction proceeds by two stages. stage 1 stage 2 reactants intermediate products The activation energy of stage 1 is 50 kJ mol–1. The overall enthalpy change of reaction is –100 kJ mol–1. Which diagram could represent the energy level diagram for the reaction? A -100 -75 -50 -25 0 25 50 75 100 reactants products progress of reaction B -100 -75 -50 -25 0 25 50 75 100 reactants products progress of reaction C -100 -75 -50 -25 0 25 50 75 100 reactants products progress of reaction D -100 -75 -50 -25 0 25 50 75 100 reactants products progress of reaction

6 Ó DHS 2012 9647/01 [Turn over 8 A student set up the hydrogen electrode shown in the diagram below. What would have to be changed to make this a standard hydrogen electrode? A the acid solution used B the temperature of the gas and of the acid solution C the pressure of the gas D the metal comprising the electrode 9 The graph below shows how the fraction of a substance, X, represented by one of the following compounds in the equilibrium mixture shown below varies with temperature at pressures of y Pa and z Pa. 4NH3(g) + 3O2(g) 2N2(g) + 6H2O(g) DH = –1267 kJ mol–1 Identify X and the correct magnitudes of y and z. X Pressure A NH3 z > y B N2 z > y C O2 y > z D H2O y > z

7 Ó DHS 2012 9647/01 [Turn over 10 The value of the ionic product of water, Kw, varies with temperature. temperature / oC Kw / mol2 dm–6 0 0.1 × 10–14 10 0.3 × 10–14 25 1.0 × 10–14 What can be deduced from this information? A Molar concentration of H+ ions decreases with temperature. B The ionic dissociation of water decreases by a factor of 10 between 0 °C and 25 °C. C The association of water molecules by hydrogen bonding increases as temperature increases. D Water is no longer a neutral liquid at temperatures below 25 °C. 11 Ozone in the earth’s atmosphere decomposes according to the equation: 2O3(g) ® 3O2(g) This reaction is thought occur via a two–step mechanism: Step 1 O3(g) O2(g) + O(g) fast, reversible Step 2 O3(g) + O(g) ® 2O2(g) slow What rate law is consistent with this mechanism? A Rate = k[O3]2 / [O2] B Rate = k[O3]2 / [O2]3 C Rate = k[O3] D Rate = k[O3]2 12 S is a transition element. The 3d sub–shell of S in the compound K[ S(C2O4)2(NH3)2] contains 3 electrons. How many unpaired electrons does S contain when it is in the elemental state? A 2 B 3 C 4 D 5

8 Ó DHS 2012 9647/01 [Turn over 13 A reaction scheme starting from aqueous copper( II) sulphate solution i s shown below. Both G and H are copper–containing species. IIIIII CuSO4(aq) NH3(aq) G excess NH3(aq) H Na4edta(aq) [Cu(edta)]2-(aq) Which of the following statements is correct? A NH3 is a ligand in reaction I. B Reaction II is a redox reaction. C H is a deep blue solution containing [Cu(NH3)3(H2O)3]SO4. D The entropy of the system increases when reaction III occurs. 14 W, X, Y and Z are elements in Period 3. W has greater electrical conductivity than Y but lower first ionisation energy than X. Y has higher melting point than W, and Z has a greater atomic radius than W. Based on this information, which of the following is a possible arrangement of these elements in increasing proton number? A W, X, Y, Z B X, Y, W, Z C Y, X, Z, W D Z, W, Y, X 15 An aqueous solution of sodium carbonate is added very slowly, till excess, to a solution containing 0.2 mol dm–3 of zinc nitrate and 0.1 mol dm–3 of silver nitrate at 25 °C. The numerical value of the solubility product of zinc carbonate at 25 °C is 1.4 ´ 10–11 and that of silver carbonate is 8.1 ´ 10–12. Which statement describes what happens in the solution? A Both zinc carbonate and silver carbonate are precipitated at the same time. B Zinc carbonate is precipitated first, followed by silver carbonate. C Silver carbonate is precipitated first, followed by zinc carbonate. D Only silver carbonate is precipitated.

9 Ó DHS 2012 9647/01 [Turn over 16 Which of the following statements about the Group VII compounds is correct? A The halogens increase in oxidising power down the group. B The Ksp values of the silver halides decrease down the group. C The lattice energy of the silver halides becomes more exothermic down the group. D The