HCI Prelim H2 CHEM P1

This document consists of 17 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 15S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Optical Mark Sheet (OMS) Data Booklet 9647/01 21 September 2016 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. 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. The use of an approved scientific calculator is expected, where appropriate.

2 © Hwa Chong Institution 2016 9647 / 01 / C2 Prelim 2016 SECTION A For each question, there are four possible answers A, B, C and D. Choose the one you consider to be correct. 1 Methyl mercaptan, CH3SH, is one of the substances responsible for bad breath and is often used to impart a smell to natural gas in a pipeline. When a sample of 10 cm 3 of CH3SH is exploded with 60 cm 3 of oxygen, the final volume of gas after burning is passed into an excess of aqueous alkali. The chemical equati on for the combustion process is shown below. CH3SH + 3O2  CO2 + SO2 + 2H2O What percentage of the final volume of gas after burning dissolves in the alkali? All gaseous volumes are measured at room temperature and pressure. A 40.0% B 28.5% C 20.0% D 14.3% 2 Figure 1 shows the first six ionisation energies of an element Q while Figure 2 shows the second ionisation energies of eight consecutive elements, including Q, in the Periodic Table. Figure 1 Figure 2 number of electrons removed Which of the elements A, B, C or D could be the element Q? 3 Which statement is not always true when an ionic solid dissolves in water? A Energy is absorbed to separate the ions in the solid. B Energy is absorbed to break the hydrogen bonding between water molecules. C Energy is released when the ions are hydrated. D Energy is released when the ionic solid dissolves completely. second ionisation energy / kJ mol1 proton number A B C D ionisation energy / kJ mol1 1 2 3 4 5 6

3 © Hwa Chong Institution 2016 9647 / 01 / C2 Prelim 2016 4 Which of the following explains the non-ideal behavior of the gases present in the reaction chamber in the Haber process? A the presence of a catalyst B the high temperature of 450 C C the high pressure of 150 atm D the strong bonds between the atoms in the nitrogen molecules 5 Which enthalpy change would best indicate the relative strengths of the intermolecular forces in liquid hydrogen halides? A bond dissociation energy B enthalpy change of formation C enthalpy change of solution D enthalpy change of vaporisation 6 CH3COCH3 and I2 react in the presence of an acid catalyst. The rate of reaction is independent of [I2] but directly proportional to [H+] and to [CH3COCH3]. Which graph is correct? A [I2] 0 time B rate 0 [H +][CH3COCH3] C [CH3COCH3] 0 rate D [H +][CH3COCH3] 0 time

4 © Hwa Chong Institution 2016 9647 / 01 / C2 Prelim 2016 7 When the system X2(g) + 3Y2(g)  2XY3(g) is at equilibrium at 500 K and 1 atm, the value of the equilibrium constant, Kp, is 100. What is the value of Kp at a pressure of 2 atm at the same temperature? A 25 B 100 C 200 D 400 8 The numerical values of the solubility product of BaSO 4, BaCO3 and Ba( IO3)2 at 25 °C are given in the table below. Compound Solubility product BaSO4 1.1  1010 BaCO3 2.6  109 Ba(IO3)2 4.0  109 An aqueous solution of BaCl2 was added slowly, until in excess, to a solution containing 0.5 mol dm3 Na2SO4, 1.0 mol dm3 Na2CO3 and 1.5 mol dm3 NaIO3 at 25 °C. What is the correct order of precipitation of the three barium salts? First to precipitate Last to precipitate A BaSO 4 BaCO 3 Ba(IO3)2 B Ba(IO3)2 BaCO 3 BaSO 4 C BaSO4 Ba(IO3)2 BaCO 3 D BaCO3 Ba(IO3)2 BaSO 4 9 What is the pH of the final solution formed when V dm3 of dilute hydrochloric acid of pH 1.0 is mixed with V dm3 of dilute sulfuric acid of pH 1.0, followed by the addition of 2V dm3 of water? A 1.1 B 1.3 C 2.0 D 4.0 10 Stomach juices have a pH of 1.0. Aspirin is a monobasic acid represented by HA ( Ka = 104 mol dm3) which dissociates into H+ and A ions. What are the relative concentrations of H +, A and HA when aspirin from a tablet enters the stomach? A [H+] > [HA] > [A] B [H+] > [A] > [HA] C [HA] > [H+] = [A] D [H+] = [A] > [HA]

5 © Hwa Chong Institution 2016 9647 / 01 / C2 Prelim 2016 11 In the construction of heart ‘pacemakers’, a tiny magnesium electrode is used which creates an electrochemical cell with the inhaled oxygen. The relevant half-equations are as follows. Mg 2+ + 2e-  Mg Eo = -2.38 V ½O2 + 2H+ + 2e-  H2O Eo = +1.23 V Under standard conditions, the cell e.m.f. would be 3.61 V. However, in the body, a potential of 3.25 V is more usual. Which of the following is an explanation for this lower e.m.f. in the body? A the pH of about 7.4 of the body fluid surrounding the electrodes B the low concentration of Mg 2+ ions surrounding the electrodes C the small size of the magnesium electrode D the large amount of oxygen inhaled 12 Ethanol fuel cells are more practical than hydrogen fuel cells since ethanol is easier to store and transport than hydrogen. Ethanol is converted to carbon dioxide when the fuel cell is operated. Which statement is correct about ethanol fuel cells? A Ethanol fuel cells can work indefinitely as long as there is a supply of ethanol and air. B For every 1 mol of ethanol oxidised, 6 mol of electrons are produced. C H + ions react with air to produce water at the anode. D The acid needs to be replenished as hydrogen ions are being used up. H2SO4 (aq) ethanol air wire connecting a pair of graphite electrodes

6 © Hwa Chong Institution 2016 9647 / 01 / C2 Prelim 2016 13 How many structural isomers of C3H4Br2 contain C=C and how many do not contain C=C? structural isomers with C=C structural isomers without C=C A 4 0 B 4 2 C 5 0 D 5 2 14 2-methylbuta-1,3-diene, CH2=C(CH3)–CH=CH2, is used as a monomer in the manufacture of synthetic rubbers. Which compound would not produce this monomer on treatment with excess concentrated sulfuric acid at 170 °C? A OH OH B C HO OH D HO OH 15 Sorbitol is a naturally-occurring compound with a sweet taste. It is often used as a substitute for sucrose by the food industry. sorbitol How many chiral centres are present in sorbitol? A 3 B 4 C 5 D 6

7 © Hwa Chong Institution 2016 9647 / 01 / C2 Prelim 2016 16 Deuterium, D, is a heavy isotope of hydrogen. Deuteriobenzene is reacted with chlorine and AlCl3 under controlled condition so that only monochlorination takes place. Assuming that the carbon-deuterium bond is broken as easily as a carbon-hydrogen bond, wh