JJC H2 Chemistry 9746 Prelim P1 Question Paper Answers

Answers to 2008 J2 Chemistry Preliminary Exams Paper 1 1. D 11. A 21. A 31. C 2. C 12. B 22. A 32. C 3. C 13. B 23. A 33. A 4. C 14. A 24. B 34. B 5. B 15. A 25. D 35. D 6. D 16. C 26. B 36. B 7. A 17. C 27. B 37. B 8. D 18. D 28. C 38. A 9. A 19. D 29. D 39. B 10. C 20. D 30. B 40. B

JURONG JUNIOR COLLEGE PRELIMINARY EXAMINATION 2008 H2 CHEMISTRY PAPER 1 9746 / 1 Wednesday 27 th August 2008 1 hour INSTRUCTIONS TO CANDIDATES: Do not open this question booklet until you are told to do so. Write your name and class on the answer sheet in the spaces provided. There are 40 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 answer sheet. Read the instructions on the answer sheet very carefully. INFORMATION FOR CANDIDATES: Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. A Data Booklet is provided. _____________________________________________________________________ This question booklet consists of 16 printed pages, including this page. [Turn over Page 2 of 16

SECTION A (30 MARKS) For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1. Potassium iodate(V) can be used as a st andard in iodine-thiosulfate titrimetry since it reacts with iodide ions according to the equation: IO3 −(aq) + 5I−(aq) + 6H+(aq) → 3I2(aq) + 3H2O(l) How many moles of s odium thiosulfate, Na 2S2O3, is needed to react with the iodine produced by 1 mole of iodate(V) ions? A 3 B 4 C 5 D 6 2. The successive ionisation energies of two elements, M and N, are given. Ionisation energy / kJ mol −1 1st 2 nd 3 rd 4 th 5 th 6 th 7 th 8th M 1090 2350 4610 6220 37800 47000 - - N 1251 2298 3822 5158 6542 9362 11018 33604 What is the formula of the compound that M and N are likely to form? A MN B M 2N2 C MN 4 D M 4N 3. Ions of two isotopes of the transition metal nickel are shown below. Ni 2+ 60 Ni2+ 58 28 28 Which one of the following statements is correct? A The Ni2+ ion has more protons than the 58 28 Ni2+ ion. 60 28 B The electronic configuration of both Ni2+ ions is 1s2 2s2 2p6 3s2 3p6 3d6 4s2. C These Ni2+ ions have the same number of el ectrons but a different number of neutrons. D The Ni2+ ion will be deflected more than the Ni2+ ion under the same magnetic field. 60 28 58 28 4. A certain mass of an ideal gas occupies a volume of 1 dm 3 at 20 oC. If the pressure remains unchanged, at what temperature will its volume be 2 dm3? A 40 oC B 293 oC C 313 oC D 586 oC Page 3 of 16

5. Which one of the following, in the solid state, has a cryst alline structure of simple molecules held together by van der Waals’ forces? A ice B iodine C graphite D silicon dioxide 6. In which pair is the bond angle in Species I greater than that in Species II? Species I Species II A BrF3 SF 6 B SF6 XeF 4 C XeF4 CO3 2− D CO3 2− BrF 3 7. You are given the following standard enthalpy changes. ΔH ,/kJ mol−1 C(graphite) + 2H2(g) → CH4(g) −75 H2(g) → 2H(g) +436 By using any other re levant data from the Data Booklet , what is the standard enthalpy change of atomisation of graphite? A +693 kJ mol−1 B +1129 kJ mol−1 C −2151 kJ mol−1 D −2587 kJ mol−1 Page 4 of 16

8. A student used the apparatus 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 = ΔT oC You are 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 kJ kg−1 K−1 What is the efficiency of this heating process? A %.ΔT c m 1000 60300 10002021 ×× × × × × C %m .ΔT c 1002021 0 60300 ×× ××× B %.ΔT c m 10010002021 300 0 60×× × × × × D %m .ΔT c 10010002021 0 60300 ×× × ××× thermometer can containing 300 g of water burner containing propan-1-ol 9. Ammonia gas and hydrogen chloride gas reac t to form ammonium chloride as shown in the equation below: NH3(g) + HCl(g) → NH4Cl(s) ΔH, = −176 kJ mol−1 The standard entropy change of this reaction is −284 J K−1 mol−1. Which of the following statements is not correct? A At room temperature, ΔG, = +84.4 kJ mol−1. B The reaction is spontaneous at 500 K. C The reaction becomes non-spontaneous at temperatures higher than 620 K. D There is an increase in order due to the formation of a solid from gases. Page 5 of 16

10. The following equilibrium exists in a system containing carbon monoxide and hydrogen gases. CO(g) + 2H2(g) = CH3OH(g) ΔH, < 0 Which of the following actions would result in an increase in the yield of methanol gas? A adding a catalyst B heating the system C liquefying the product by cooling D lowering the pressure of the system 11. The electrolysis of aqueous sodium sulfate, Na 2SO4, was carried out using inert electrodes in the apparatus below. It is observed that bubbles of colourless gases were liberated at the end of each electrode. Which of the following could give the co rrect volumes of the gases collected, in dm 3, at the end of the experiment? at positive electrode at negative electrode A 3.0 6.0 B 6.0 3.0 C 4.0 6.0 D 6.0 4.0 negative electrode positive electrode aqueous sodium sulfate Page 6 of 16

12. The titration curve below shows the reaction between a solution of a weak monoprotic acid, HX, and aqueous sodium hydroxide. What is the value of K a, in mol dm−3, for this acid HX? A 1.0 × 10−3 B 1.0 × 10−5 C 1.0 × 10−6 D 1.0 × 10−9 2 4 6 8 12 10 0 14 0 50 10 20 30 40 Volume of 0.10 mol dm−3 NaOH(aq) added / cm3 13. The solubility product values of two Group II fluorides, at 25 oC, are given in the table below. Group II fluorides m−9 Ksp / mol3 d CaF2 x 10−11 3.9 BaF2 7 x 10−6 1. A solution L contains 0.100 mol dm −3 of calcium chloride and 0.100 mol dm −3 of barium chloride. What would happen when equal volumes of solution L and 0.00500 mol dm −3 of sodium fluoride are mixed together? A No precipitate is formed. B Only a precipitate of CaF2 is formed. C Only a precipitate of BaF2 is formed. D Both precipitates of CaF2 and BaF2 are formed. Page 7 of 16

14. The rate equation for this reaction W + 2X + Y → Z is given below: Rate = k[X]2[Y] If the concentration of W is tripled, the concentration of X is halved and the concentration of Y is doubled, by what factor is the rate of reaction being changed? A 0.5 B 1.0 C 2.0 D 4.0 15. Which of the following elements has the same oxidation number in all of its known compounds? A aluminium B nitrogen C carbon D chlorine 16. The following graphs show how three proper ties of the elements, Na to P, and their compounds, vary with proton number. Graph 1 Graph 2 Graph 3 What properties are shown by the three graphs? Graph 1 Graph 2 Graph 3 A Melting point of oxide Melting point of chloride Conductivity of element B Melting point