HCI H2 CHEM P1 Prelim

This document consists of 20 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 13S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Optical Mark Sheet (OMS) Data Booklet 9647/01 25 September 2014 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 2014 9647 / 01 / C2 Prelim 2014 SECTION A 1 Consider the following half equations. MnO4  + 8H+ + 5e  Mn2+ + 4H2O C2O4 2  2CO2 + 2e To determine the concentration of Ca 2+ ions in river water sample, 1.00 cm 3 of the water sample was first treated with excess aqueous Na 2C2O4. The CaC 2O4 precipitate formed was filtered and treated with dilute aqueous H 2SO4. The C 2O4 2 ions released into the solution required 10.00 cm3 of 2.00  10–5 mol dm–3 acidified KMnO4 for complete reaction. What was the concentration of Ca2+ in the river water sample? A 5.00  10–4 mol dm–3 B 8.00  10–5 mol dm–3 C 5.00  10–7 mol dm–3 D 8.00  10–8 mol dm–3 2 Chromium has four naturally occurring stable isotopes: 50Cr, 52Cr, 53Cr, and 54Cr. Which statement about its ions is correct? A 52Cr3+ ion has less protons than 54Cr3+ ion. B The electronic configuration of 52Cr3+ ion is 1s22s22p63s23p63d24s1. C The electronic configurations of 52Cr3+ ion and 53Cr3+ ion are different. D 50Cr3+ ion shows a greater angle of deflection than 52Cr3+ ion in an electric field. 3 The successive ionisation energies of two elements, P and Q, are given below. Ionisation energies / kJ mol−1 1st 2nd 3rd 4th 5th 6th 7th 8th P 740 1450 7720 10540 13630 18020 21700 25660 Q 1011 1907 2910 4960 6270 21270 25431 29872 What is the formula of the compound formed when P reacts with Q? A P2Q3 B P3Q2 C P2Q5 D P5Q2

3 © Hwa Chong Institution 2014 9647 / 01 / C2 Prelim 2014 4 In an experiment, 2.0 g of a gas Y at 273 C was found to occupy the same volume as 1.5 g of nitrogen gas at 298 C. Both gases were at the same pressure. What is the relative molecular mass of the gas Y? A 2985.1 282730.2   B 2730.2 282985.1   C )273298(5.1 28)273273(0.2   D )273273(0.2 28)273298(5.1   5 The Ellingham diagram plots the free energy change of a reaction as a function of temperature, as given by the equation G = H  TS. A study was done involving the oxides of silicon. Silicon reacts with oxygen gas as shown: Reaction 1: 2Si(s) + O2(g)  2SiO(g) Reaction 2: Si(s) + O2(g)  SiO2(s) Which Ellingham diagram correctly corresponds to reaction 1 and reaction 2? A B C D

4 © Hwa Chong Institution 2014 9647 / 01 / C2 Prelim 2014 6 Use of the Data Booklet is relevant to this question. A student connects a Zn 2+/Zn half-cell to a Fe 3+/Fe2+ half-cell. The voltage measured across the electrodes is found to be +1.50 V. Which of the following could be a reason for the discrepancy between the calculated E cell and the measured value? A Water is added to the Zn2+/Zn half-cell. B Water is added to the Fe3+/Fe2+ half-cell. C The piece of zinc in the Zn2+/Zn half-cell used is too small. D A small amount of NaCN(aq) is added to the Fe3+/Fe2+ half-cell. 7 The diagram below shows the sodium -sulfur secondary cell, which is a type of molten -salt battery constructed from liquid sodium and sulfur. Cell seal Electrode J Sodium Electrolyte Sulfur Electrode K During discharge, sulfur is reduced to polysulfide ion, Sx 2. Which statement about the cell is incorrect? A The cell can be operated at room temperature. B Electrode J is the negative terminal during discharging. C The cell is potentially explosive if the seal is broken and water enters the cell. D The polarities of electrodes J and K remain the same during charging and discharging.

5 © Hwa Chong Institution 2014 9647 / 01 / C2 Prelim 2014 8 A pure sample of NH 3(g) is introduced into an evacuated vessel of constant volume. This vessel is maintained at constant temperature such that the equilibrium below is established. 2NH3(g)  N2(g) + 3H2(g) The value of the final pressure is then found to be 40 % greater than if only NH3 were present. What is the mole fraction of H2 in the reaction mixture? A 0.14 B 0.29 C 0.43 D 0.72 9 The graph below shows how the percentage of product present at equilibrium varies with temperature and pressure for a reaction. Which reaction could the graph represent? A 4Fe (s) + 3O2 (g)  2Fe2O3 (s) H = −1644 kJ mol−1 B 2C (s) + O2 (g)  2CO (g) H = −222 kJ mol−1 C N2O4(g)  2NO2(g) H = +57 kJ mol−1 D CO(g) + Cl2(g)  COCl2(s) H = +86 kJ mol−1 10 Dimethyl sulfoxide, DMSO, is an organic solvent which can dissolve polar and non -polar compounds. Ethanoic acid ionises in DMSO in the following manner: CH3CO2H  CH3CO2  + H+ The pKa of ethanoic acid in DMSO is 12.6. What is the concentration of H + ions at equilibrium if 1.0  102 mol of ethanoic acid was dissolved in 500 cm3 of DMSO? A 5.0  108 mol dm3 B 7.1  108 mol dm3 C 2.5  1015 mol dm3 D 5.0  1015 mol dm3 Percentage of product (T + 20) °C T °C Pressure

6 © Hwa Chong Institution 2014 9647 / 01 / C2 Prelim 2014 11 Solid calcium hypochlorite pellets, Ca(C lO)2(s), are added to swimming pools to form HClO(aq), which kills disease-causing bacteria and algae. Ca(ClO)2(s)  Ca2+(aq) + 2ClO(aq) ClO(aq) + H2O(l)  HClO(aq) + OH(aq) What is the effect on the solubility of calcium hypochlorite and bacterial growth when pH decreases? Solubility of calcium hypochlorite Effect on bacterial growth A Decreases More favourable B Decreases Less favourable C Increases More favourable D Increases Less favourable 12 2.0 mol dm–3 of 2-bromo-2-methylpropane was reacted with an excess of hot aqueous sodium hydroxide. The following results were obtained. (CH3)3CBr + OH  (CH3)3COH + Br Time/min 0 15 40 80  [(CH3)3COH]/ mol dm–3 0 0.5 1.0 1.5 2.0 What is the value of the rate constant? A 8.66  10–3 B 1.73  10–2 C 2.77  10–2 D 4.62  10–2 13 Based on the information below, what could element M be? M O2 white solid water colourless solution white ppt, insoluble in excess white ppt NaOH(aq) H2SO4(aq) A lead B calcium C magnesium D zinc

7 © Hwa Chong Institution 2014 9647 / 01 / C2 Prelim 2014 14 HCl is stable to heat, but HI decomposes into its elements when heated. What is the reason for this difference? A HI is a stronger reducing agent than HCl. B H–Cl bond is more polar than H–I bond. C H–Cl bond is stronger than H–I bond. D HI is more volatile than HCl. 15 Photographic film contains a mixture of silver chloride and silver bromide, which absorb light to undergo a ‘self-redox’ process to produce silver metal and halogens. During the development of the film, a solution of aqueous sodium thiosulfate is used to dissolve the unreacted silver halides. Which statement conce