MI Prelim 2008 H2 Chemistry Paper 1

Class Adm No Candidate Name: This question paper consists of 15 printed pages. [Turn over Preliminary Examinations 2008 Pre-university 3 H2 CHEMISTRY 9746 / 01 Tuesday 9 Sep 2008 1h Additional materials: OMR Data Booklet READ THESE INSTRUCTIONS FIRST 1. Do not turn over this question paper until you are told to do so. 2. Write your name, class and index number in the spaces provided at the top of this page and on any separate answer paper used. 3. Attempt ALL the questions in Section A and B. 4. All answers are to be shaded on the OMR form provided using a 2B pencil. 6. Hand in your answers to the paper (OMR form) and question paper separately. INFORMATION FOR CANDIDATES No extra time will be given for shading of OMR form.

SECTION A (30 MARKS) Answer all questions on the OMR form provided For each question, there are four possible answers, A, B, C and D. Choose the one you consider correct. 1. Lithium forms compounds which are used in dry cells and storage batteries and in high temperature lubricants. It has two naturally occurring isotopes, 6Li (isotopic mass = 6.015121 amu) and 7Li (isotopic mass = 7.016003 amu). Lithium has an atomic mass of 6.9409 amu. What is the percentage abundance of the 6Li isotope? A 7.503% B 46.16% C 86.66% D 92.50% 2. In one experiment, 45.0cm 3 of 0.2moldm-3 aqueous M2+ solution has reacted with 15.0cm3 of 0.1 moldm-3 aqueous acidified potassium dichromate (VI) solution. What is the oxidation state of M after the reaction? A +3 B +4 C +5 D +7 3. Which one of the following is not a redox reaction? A Br2 + SO2 + 2H2O → SO4 2- + 4H+ + 2Br– B SnCl2 + HgCl2 → Hg + SnCl4 C Cu2O + H2SO4 → CuSO4 + Cu + H2O D 2CrO4 2- + 2H+ → Cr2O7 2– + H2O 4. A mixture of 8.0g of a monoatomic gas X and an unknown quantity of diatomic gas Y has a volume of V m 3 at s.t.p. When 20.0g of gas X is added to the mixture, under the same conditions, the volume of the mixture is 2V m3. Calculate the quantity of gas Y in the mixture. [Relative molecular mass: X = 4, Y =1] A 2g B 3g C 5g D 6g 2

5. A new boron hydride, BxHy, has been isol ated. To find its molar mass, you measure the pressure of the gas in a known volume at a known temperature. The following experimental data are collected: Mass of the gas = 12.5mg Pressure of the gas = 3306 Pa Temperature = 25 °C Volume of the flask = 125 mL Which formula corresponds to the calculated mass? A B 2H6 B B 4H10 A B 5H9 A B 6H10 6. Which one of the following is the electron arrangement of the strongest reducing agent? A 1s2 2s2 2p5 B 1s2 2s2 2p6 3s2 C 1s2 2s2 2p6 3s2 3p5 D 1s2 2s2 2p6 3s2 3p6 4s2 7. Which of the following molecules / ions has non-zero dipole moments? A BF 3 B cis-HClC=CHCl C CO 2 D ICl4 - 8. Which one of the equations below represents a reaction that is feasible at all temperatures? A P(s) → Q(s) + R(g) endothermic B 2L(g) + M(g) → 2N(g) exothermic C S(g) → 2T(g) exothermic D A(g) + B(g) → C(g) endothermic 3

9. Enthalpy changes for the following reactions can be determined experimentally: N2(g) + 3H2(g) → 2NH3(g) ΔH = -91.8 kJ 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l) ΔH = -906.2 kJ H2(g) + ½O2(g) → H2O ( l ) ΔH = -241.8 kJ What is the enthalpy change of formation of NO(g)? A +90 kJ B +180 kJ C +361 kJ D +1270 kJ 10. Calcium hydride, CaH 2, is an ionic compound that contains H– ions. The Born–Haber cycle for the formation of CaH2 from Ca(s) and H2(g) does not involve A the sublimation energy of calcium. B the first ionisation energy of calcium. C the atomisation energy of hydrogen. D the ionisation energy of hydrogen. 11. Which of the following statements regarding the half-life of a first-order reaction is true? A The half-life is affected by pressure. B The half-life depends on the concentration of the reactants. C The half-life is shorter at lower temperature. D At the end of the fourth half-life, the percentage of element left is 6.25% of original quantity. 4

12. Hydrogen sufide reacts with water according to the following equilibrium: H2S(aq) + 2H2O(l) 2H3O+(aq) + S2-(aq) Which of the following changes would not influence the concentration of S2- ions in the above equilibrium mixture? A Addition of ammonia B Addition of alumnium sulphate C Addition of sodium carbonate D Reduction of volume of container 13. For the reaction A (g) + B (g) C (g) + D (g), suppose that the concentrations of these gases were the following in an equilibrium mixture: [A] = 0.5 , [B] = 4.0 , [C] = 6.0 , and [D] = 8.0 in a 1 dm3 container. How many moles of D would have to be added to the mixture to raise the concentration of A to 1.0 mol dm -3? A 0.034 mol B 0.5 mol C 6.04 mol D 12.1 mol 14. Which one of the following will produce a saturated solution with the highest pH? A barium hydroxide B beryllium hydroxide C calcium hydroxide D strontium hydroxide 15. The solubility of M 2Y3 is 1 x 10-10 mol dm-3. What is the Ksp for the compound? A 1 x 10 -20 B 6 x 10 -28 C 1 x 10-48 D 1 x 10 -56 5

16. An acid-base titrations is carried out between HX and NaOH. Similar titration is also carried out between HY and NaOH. The change in pH is recorded and plotted as graphs shown below. Which one of the following statements about a solution of HX is correct? A It is less concentrated and contains a weaker acid than the solution of HY. B It is more concentrated and contains a stronger acid than the solution of HY. C It is more concentrated and contains a weaker acid than the solution of HY. D It is less concentrated and contains a stronger acid than the solution of HY. 17. A hydrogen-oxygen fuel cell currently in use generated a voltage of about 0.9V at a temperature between 70 oC to 140oC. Calculate the voltage for the hydrogen-oxygen fuel cell under standard conditions. A - 0.43 V B - 0.83 V C +0.40V D +1.23 V 6

18. The table below contains the reduction potential values for copper and mercury species. Half-equations E / V φ Cu2+ (aq) + e Æ Cu+ (aq) +0.15 Cu+(aq) + e Æ Cu (s) +0.52 Hg2+(aq) + e Æ Hg+(aq) +0.91 Hg+(aq) + e Æ Hg(l) +0.80 Using these data, which one of the following can be predicted? A Both Cu(I) and Hg(I) undergo disproportionation. B Only Cu(I) undergoes disproportionation. C Only Hg(I) undergoes disproportionation. D Neither Cu(I) nor Hg(I) undergoes disproportionation. 19. The following cell is set up to obtain a pure copper by electrolysis as shown in the diagram below. Pure copper Copper (II) sulphate) solution Copper argentums alloy When a current of 40A flows through the circuit for 26.80 minutes, the mass of the anode decreases by 26.47g. What is the percentage composition of copper in the copper alloy? A 50% B 60% C 70% D 80% 7

20. A reaction scheme involving chromium is shown below: Cr2O7 2-(aq) V FeSO4/H+ Which of the following statement is incorrect? A The oxidation states of chromium shown in the above reaction scheme are +2, +3 and +6. B Only step X will produce a precipitate and a gas. C Steps V, W and Z will produce a colour change. D Steps X and Y will involve a change in the oxidation state of chromium. 21. The compound cis-retinal is shown below. Which one of the labelled bonds leads to the prefix in the name? B [Cr(H2O)6 ]3+(aq) Y NaO [Cr(H2O)6 ]2+(aq) W Zn/ [Cr(OH)6 ]3-(aq) Z H2O2 H+ H [Cr(OH)3(H2O)3 ]2+ (s) X Na2CO3 CrOH4 2-(aq) 8

22. One mole of Compound X reacts with 1 mole of hydrogen gas in a catalytic hydrogenat