2020 HCI Prelim Paper 1 Question Paper

This document consists of 16 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 19S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 9729/01 21 September 2020 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 Answer Sheet as shown below. There are 30 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 Answer Sheet. Read the instructions on the Answer Sheet very carefully. 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.

© Hwa Chong Institution 2020 9729/01/C2Prelim 2020 [Turn over 2 1 Use of the Data Booklet is relevant to this question. In which pairs do both species have different number of unpaired p electrons? A Al2− and O+ B N and Cl2+ C C and Cl+ D B− and S+ 2 Four substances have the physical properties shown. Which substance exists as a simple molecular solid at room temperature? melting point/ C electrical conductivity solubility in water A −7 does not conduct slightly soluble B 46 does not conduct insoluble C 420 conducts insoluble D 782 does not conduct soluble 3 Which statement about covalent bonds is incorrect? A The electron density in a  bond is highest along the axis between the two bonded atoms. B Covalent bonds can occur together with ionic bonds in the same compound. C A triple bond consists of one  bond and two  bonds. D A  bond restricts rotation about the  bond axis. 4 Which statement about an ideal gas is correct? A The density of an ideal gas at constant temperature is inversely proportional to the pressure. B One mole of any ideal gas occupies the same volume under the same conditions of temperature and pressure. C The volume of a given mass of an ideal gas is doubled if its temperature is raised from 25 C to 50 C at constant pressure. D Adding an inert gas to an ideal gas at constant volume and temperature will increase the partial pressure of the ideal gas.

© Hwa Chong Institution 2020 9729/01/C2Prelim 2020 [Turn over 3 5 When 10 cm3 of a gaseous organic compound were completely burnt in an excess of oxygen, 30 cm3 of carbon dioxide and 5 cm 3 of nitrogen were formed, all volumes being measured at the same temperature and pressure. Which could be the formula of the organic compound? A C2H6N2 B C2H7NO C C3H7N2 D C3H5N 6 A saturated solution of XeF2 (Mr = 169) contains 25.0 g dm–3 of XeF2. In an experiment, 15.20 cm 3 of the XeF 2 solution is required to completely react with 10.0 cm 3 of a nother solution containing 0.150 mol dm –3 of M 2+ (M is a metal). XeF 2 is converted to Xe. What is the oxidation state of M after the reaction? A +3 B +4 C +5 D +6

© Hwa Chong Institution 2020 9729/01/C2Prelim 2020 [Turn over 4 7 The diagram represents the melting points of four consecutive elements in the third period of the Periodic Table. The sketches below represent another two properties of these elements. What are properties X and Y? property X property Y A electrical conductivity ionic radius B first ionisation energy atomic radius C pH of the chlorides with water effective nuclear charge D pH of the oxides with water highest oxidation number in oxides property Y 0     property X 0     melting point/ C 0 proton number     proton number proton number

© Hwa Chong Institution 2020 9729/01/C2Prelim 2020 [Turn over 5 8 X and Y are two different Group 2 metals. Some of their applications are described below. The oxide of X is used as a refractory lining materials in kilns. The carbonate of Y is used as a building material. It can be heated to form compound Z. When Z is hydrated, the resulting compound is used agriculturally to treat soils. Which statement about X and Y is correct? A X reacts with cold water more quickly than Y. B The reducing power of X is higher than that of Y. C The nitrate of X decomposes at a lower temperature than the nitrate of Y. D The numerical value of the lattice energy of the oxide of X is smaller than that of the oxide of Y. 9 The element astatine lies below iodine in Group 17 of the Periodic Table. What will be the properties of astatine? 1 It forms diatomic molecules which dissociate more readily than chlorine. 2 Hydrogen astatide is less stable to heat than hydrogen iodide. 3 Silver astatide is soluble in aqueous ammonia. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only 10 A sample of chlorine dioxide is completely decomposed in a sealed container at constant pressure. ClO2(g)  ½Cl2(g) + O2(g) What will cause a decrease in the entropy of the system while keeping the pressure constant? A increase the volume of the container B increase the temperature of the system C add an inert gas into the system at constant temperature D remove chlorine from the system at constant temperature

© Hwa Chong Institution 2020 9729/01/C2Prelim 2020 [Turn over 6 11 The following table show s the temperature rise on mixing acids with aqueous sodium hydroxide. mixture temperature rise/ C 25 cm3 of 1 mol dm−3 HCl(aq) + 25 cm3 of 1 mol dm−3 NaOH(aq) w 25 cm3 of 1 mol dm−3 CH3CO2H(aq) + 25 cm3 of 1 mol dm−3 NaOH(aq) x 50 cm3 of 1 mol dm−3 HCl(aq) + 50 cm3 of 1 mol dm−3 NaOH(aq) y 50 cm3 of 1 mol dm−3 CH3CO2H(aq) + 50 cm3 of 1 mol dm−3 NaOH(aq) z Which are the relative values of temperature rise? A w = y > x = z B w > y > x > z C y = z > w = x D y > w > z > x 12 Which statement about a first-order reaction is correct? A The reactant concentration decreases linearly with time. B The reactant concentration decreases exponentially with time. C The rate of reaction remains constant as the reaction proceeds. D The rate of reaction increases exponentially as the reaction proceeds.

© Hwa Chong Institution 2020 9729/01/C2Prelim 2020 [Turn over 7 13 Which statements are correct when a catalyst is added to a sample of reacting molecules? 1 The rate constant remains the same but the rate of reaction increases. 2 The catalyst allows the reacting molecules to react via an alternative pathway with a lower activation energy, hence rate of reaction increases. 3 The Boltzmann distribution changes from curve X to Y, resulting in a greater proportion of molecules having energy above the activation energy, Ea, hence rate of reaction increases. A 2 only B 1 and 2 only C 1 and 3 only D 2 and 3 only

© Hwa Chong Institution 2020 9729/01/C2Prelim 2020 [Turn over 8 14 The graph below shows how the yield of an industrially manufactured compound, X, changes with temperature under five different operating pressures. In this reaction, X is the only gaseous product formed from gaseous reactants. What can be inferred from the graph above? 1 The forward reaction is exothermic. 2 The balanced equation for the reaction involves a greater number of moles of gaseous reactants than the gaseous product X. 3 The industrial conditions are decided by taking into consideration the rate of the reaction as well a