HCI H2 CHEM P1 ANSWERS Prelim

This document consists of 14 printed pages. HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 10S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 9647/01 23 September 2011 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

2 © Hwa Chong Institution 2011 9647 / 01 / JC2 Prelim 2011 Section A For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1 Mixtures of argon and another gas are commonly used during welding. One such gaseous mixture has a density of 1.82 g dm −3 at s.t.p. What could be the other gas in this mixture? [Density of argon = 1.78 g dm −3 at s.t.p.] A Carbon dioxide B Oxygen C Nitrogen D Helium 2 X is an organic iron compound containing only Fe, C and H. When a 0.944 g sample of X was subjected to complete combustion, 2.23 g of CO2 and 0.457 g of H2O were formed. What is the empirical formula of X? A FeCH B FeC 2H C Fe2C5H2 D FeC10H10 3 Some isotopes are unstable and undergo nuclear (radioactive) reactions. In one type of reaction, an unstable nucleus assimilates an electron from an inner orbital of its electron cloud. The net effect is the conversion of a proton and an electron into a neutron. Which of the following describes this type of reaction? A 11C  12C B 111I  111Te C 76Br  75Br D 76Kr  75Br 4 In which of the following pairs does the first substance have a higher melting point than the second? First substance Second substance A CH3CH2OCH3 CH 3CH2NHCH3 B (CH3)3CH CH 3CH2CH2CH3 C RbCl KC l D C O OH OH C O OH OH

3 © Hwa Chong Institution 2011 9647 / 01 / JC2 Prelim 2011 5 A fixed amount of an ideal gas is contained in a frictionless gas syringe. For a period of t seconds, the volume of the syringe is increased at a constant rate. The temperature within the syringe is constant throughout. Which of the following graphs correctly shows how the pressure in the syringe changes within the t seconds? A B C D 6 When water vaporizes, 40.7 kJ mol1 of heat enthalpy is required. What is the entropy change when 72 g of water boils at 100 C? A 436 J K1 B 109 J K1 C +109 J K1 D +436 J K1 7 Trace levels of radioactive isotope caesium-134 is believed to have travelled by air to China from the quake-damaged Fukushima Daiichi Nuclear Power Plant in Japan. Given that the radioactive decay of caesium-134 is a first-order reaction with the rate constant k = 0.347 year 1, what is the time taken for caesium-134 to reach one-eighth of its initial concentration? A 2 years B 4 years C 6 years D 8 years time / s0 t time / s0 t time / s 0 t time / s0 t pressure / Pa pressure / Pa pressure / Pa pressure / Pa

4 © Hwa Chong Institution 2011 9647 / 01 / JC2 Prelim 2011 8 Consider the following reaction: E + 3F  EF3 The mechanism involves the following steps: 2F Ý F 2 fast E + F2  EF2 slow EF2 + F  EF3 fast Based on the information, what is the rate equation for this reaction? A Rate = k[F] 2 B Rate = k[E][F]2 C Rate = k[E][F]3 D Rate = k[E][F2] 9 Consider the equilibrium 3J2(g) + 2KJ(g) Ý 2KJ4(g). When 4 mol of KJ4 was put into a 2 dm 3 container and heated, the equilibrium mixture contained 0.8 mol of KJ. What is the numerical value of the equilibrium constant, K c? A 74.1 B 9.23 C 1.16 D 0.108 10 Phenolphthalein (C20H14O4) is an organic compound used as an acid-base indicator. Why does phenolphthalein, which is colourless in acidic solutions, turn pink in alkaline solutions? A It is oxidised to a pink compound by hydroxide ions. B It is reduced to a pink compound by hydroxide ions. C It forms a pink anion by loss of H+ ions. D It forms a pink cation by gain of H+ ions.

5 © Hwa Chong Institution 2011 9647 / 01 / JC2 Prelim 2011 11 The numerical value of the solubility product of calcium fluoride is 3.9  1011. Given that HF is a weak acid, which di agram shows how the solubility of CaF 2 will vary with pH at constant temperature? A B C D 12 Use of the Data Booklet is relevant to this question. The AgCl / Ag reference electrode is based on the following reaction: AgCl + e  Ý Ag + Cl The reduction potential of the Fe 2+ / Fe couple was found to be 0.64 V when measured using the AgCl / Ag reference electrode. What is the reduction potential of the AgCl / Ag electrode with respect to the standard hydrogen electrode? A 0.20 V B +0.20 V C 1.10 V D +1.10 V solubility pH solubility pH solubility pH solubility pH

6 © Hwa Chong Institution 2011 9647 / 01 / JC2 Prelim 2011 13 The graph below shows the variation in the boiling points for eight consecutive elements in the Periodic Table, all with atomic number between 10 and 20. Which of the following statements is true? A Element D forms an acidic oxide. B Element G does not conduct electricity. C Element A and beryllium are in the same group. D The element immediately preceding A has a smaller atomic radius than A. 14 Which of the following statements is true about magnesium and barium and their compounds? A Magnesium carbonate is more stable to heat compared to barium carbonate. B Magnesium has a lower tendency to form complex ions compared to barium. C The lattice energy of magnesium oxide is more negative than the lattice energy of barium oxide. D The pH of a saturated solution of magnesium hydroxide is higher than the pH of a saturated solution of barium hydroxide. 15 A mixture of iodine and chlorine was reacted with excess sodium thiosulfate solution.  The resulting mixture was treated with excess aqueous barium nitrate. Precipitate W formed was filtered off and washed with distilled water.  The filtrate was treated with excess silver nitrate. The precipitate formed was filtered off and washed with excess aqueous ammonia.  The mixture was again filtered, leaving behind precipitate X. Which anion was present in each of the precipitates respectively? Precipitate W Precipitate X A SO4 2 C l  B SO4 2 I  C Cl  I  D I  SO4 2– Atomic number A B C D E F G H Boiling point B A D C E H G F

7 © Hwa Chong Institution 2011 9647 / 01 / JC2 Prelim 2011 16 Which of the following particles, on losing an electron, contains five unpaired d-electrons? A Fe2+ B Cr+ C Mn2+ D Ni+ 17 Palladium compounds are widely used as catalyst in coupling reactions. One such compound is (dppf)PdCl2 with its structure shown below. P P Fe RR RR Pd Cl Cl What does the structure of (dppf)PdC l2 suggest about the nature of the bonding between Pd and the phosphorus atoms, and the oxidation state of Pd? nature of bonding oxidation state A covalent 0 B ionic 0 C covalent +2 D ionic +2 18 Cortisol is the major h