HCI H2 Chem 2013 Prelim P1 QP

This document consists of 14 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 12S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Optical Mark Sheet (OMS) Data Booklet 9647/01 25 September 2013 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Complete the information on the optical mark sheet (OMS) as shown below. 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 OMS. 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. Write your name Write and shade your NRIC or FIN number Write your CT group 551

2 © Hwa Chong Institution 2013 9647 / 01 / C2 Prelim 2013 Section A For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1 A mixture containing only aluminium oxide, A l2O3, and copper( I) oxide, Cu 2O, weighs 2.02 g. When heated under a s tream of hydrogen, A l2O3 is unchanged while Cu 2O is reduced to metallic copper and steam. Cu2O(s) + H2(g)  2Cu(s) + H2O(g) If the residue weighs 1.88 g, what is the percentage by mass of Cu2O in the mixture? [Mr : Al2O3, 102.0; Cu2O, 143.0] A 12 % B 55 % C 59 % D 62 % 2 A constituent of wood preservative i s manufactured by heating the ore chromite, FeCr 2O4, with sodium carbonate in air. 4FeCr2O4 + 8Na2CO3 + 7O2  8Na2CrO4 + 2Fe2O3 + 8CO2 What are the changes in oxidation number of chromium and iron in this reaction? Change in oxidation number of chromium Change in oxidation number of iron A +1 0 B +2 0 C +2 +1 D +3 +1 3 Use of the Data Booklet is relevant to this question. Copper and magnesium are metals that are widely used in alloys. Each metal forms many compounds containing an M2+ ion. Which statement concerning the atom and ion of these two elements is correct? A Cu2+ ion has a smaller ionic radius than Mg2+ ion. B Cu atom has a lower first ionization energy than Mg atom. C Cu atom has two more occupied electron shells than Mg2+ ion. D Cu2+ ion has a larger angle of deflection than Mg 2+ ion when both ions are passed through the same electric field. 552

3 © Hwa Chong Institution 2013 9647 / 01 / C2 Prelim 2013 4 Lecithin is an emulsifier that is used in chocolate to give a smooth texture. Which of the following statements about lecithin is correct? A It can form dispersion forces with non-polar molecules present in chocolate. B It can form hydrogen bonds between its own molecules. C All bond angles surrounding each carbon atom are 109. D It does not contain delocalized electrons. 5 A given mass of a diatomic gas was placed in a vessel of fixed volume V cm3 at a pressure p atm and temperature T C. Assuming ideal behavior, which of the following changes would cause the density of the gas to double? A Cooling the gas to ½ T C. B Adding a catalyst that causes the gas to dissociate into gaseous atoms at T C. C Adding an equal mass of the same gas into the same vessel at T C. D Connecting the vessel to an identical vessel containing the same mass of the diatomic gas at T C and p atm. 6 At all temperatures below 491 C, black HgS converts spontaneously to red HgS. HgS(s) (black)  HgS(s) (red) S = 5.5 J mol1 K1 What is the standard enthalpy change for the conversion of black HgS to red HgS? A +2.7 kJ mol1 B +4.2 kJ mol1 C 2.7 kJ mol1 D 4.2 kJ mol1 553

4 © Hwa Chong Institution 2013 9647 / 01 / C2 Prelim 2013 7 The rate equation for the reaction between hydrogen gas and iodine gas is given below. Rate = k[H2][I2] Kinetics studies have detected odd electron species in the course of the reaction. Which of the following mechanisms is consistent with the information provided above? A H2(g) + I2(g) 2HI(g) (slow) B I2(g) 2I(g) (fast) H2(g) + I(g) H2I(g) (fast) H2I(g) + I(g) 2HI(g) (slow) C I2(g) 2I(g) (fast) H2(g) + I(g) H2I(g) (slow) H2I(g) + I(g) 2HI(g) (fast) D I2(g) 2I(g) (slow) H2(g) + I(g) H2I(g) (fast) H2I(g) + I(g) 2HI(g) (fast) 8 The remains of an ancient building were recently uncovered in Rome. Its approximate age was determined by measuring the amount of radioactive 14C that remains and it was found that 15.5% of the original amount of 14C remains. Assuming that 14C decays via a first -order process and given that its half life is 5730 years, what is the approximate age of the ancient building? A 1.1 x 104 years B 1.5 x 104 years C 1.7 x 104 years D 2.3 x 104 years 9 1.00 mol of CH 4, 2.00 mol of H 2S, 1.00 mol of CS 2, and 2.00 mol of H 2 were placed in a 500 cm3 reaction vessel at 960 oC. The mixture was allowed to reach equilibrium according to the following equation. CH4(g) + 2H2S(g) CS2(g) + 4H2(g) At equilibrium, the concentration of CH4 was 1.12 mol dm–3. What is the value of the equilibrium constant, Kc, at 960 oC? A 1.64 x 103 B 1.20 C 0.836 D 6.10 x 10–4 554

5 © Hwa Chong Institution 2013 9647 / 01 / C2 Prelim 2013 10 The relationship between pKw of H2O and temperature is shown below. Given that the bond energies of the oxygen –hydrogen and oxygen –deuterium bond are 462 kJ mol–1 and 466 kJ mol–1 respectively, which of the following statements is incorrect? [Deuterium, D = 2H] A H2O is neutral at 280 K. B At 330 K, the pH of H2O is approximately 6.55. C The auto-ionisation of H2O is an endothermic reaction. D The graph for D2O lies below the graph for H2O. 11 The reaction between Pb 2+(aq) and I–(aq) was investigated. The graph below shows the total concentration of soluble lead(II)-containing species against the concentration of iodide ions. Which of the following conclusions can be inferred from the graph above? A When 0 < [I–] < x, a lead(II) complex is being formed. B When [I–] > x, solid lead(II) iodide dissolves. C When [I–] = x, the amount of solid lead(II) iodide is at its minimum. D When [I–] = x, the concentration of Pb2+(aq) is 0 mol dm–3. pKw T/ K 555

6 © Hwa Chong Institution 2013 9647 / 01 / C2 Prelim 2013 12 The diagram below shows the presence of a water droplet on a piece of iron, together with an unknown metal C which is incorporated into the iron piece to prevent it from corrosion. Which of the following descriptions of the rusting of iron is correct? A The cathodic site is located at point D in the diagram. B When metal C is zinc, iron behaves as the anode. C When metal C is copper, corrosion of iron will not occur. D The key reaction involving oxygen during rusting is O2 + 2H2O + 4e– 4OH−. 13 Which of the following chlorides gives a solution of the highest pH when added to water? A NaCl C CH3NH3Cl B MgCl2 D SiCl4 14 Magnesium nitrate and barium nitrate were heated strongly in separate experiments. Which of the following information will distinguish the two compounds? A Colour of the residual solid B Solubility of the residual solid in water C Colour of the gas evolved D Whether the gas evolved rekindles a glowing splint 15 Which of the following trends concerning halogens and their compounds is correct? A The boiling point of the hydrogen halides increases in the order HF < HCl < HBr < HI. B The thermal stability of t