HCI Prelim P1

HWA CHONG INSTITUTION C2 PRELIMINARY EXAMINATION 8872 H1 CHEMISTRY PAPER 1 Multiple Choice 29 September 2009 50 minutes   Do not open this booklet until you are told to do so. READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Complete the information on the optical mark sheet (OMS) as shown below. Write your CT group Write your CT group Write and shade your NRIC or FIN number Write your name There are thirt y 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. This document consists of 10 printed pages.

HCI(College) 2009 8872/01/C2 Prelim/09 2 Section A For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1 The relative abundances of the isotopes of a sample of titanium are shown in the table below. What is the relative atomic mass of titanium in this sample? Relative Isotopic Mass 46 47 48 49 50 Relative Abundance 11.2 10.1 100.0 7.3 7.0 A 47.92 B 47.91 C 47.90 D 47.89 2 In the middle of the 15 th century, ‘black powder’ was widely used by the Arabs as propellant for muzzle-loading cannons. ‘Black powder’ consis ted of a mixture of potassium nitrate, sulfur and charcoal (carbon) in the molar ratio shown in the equation below. 2KNO3 (s) + S (s) + 3C (s)  K2S (s) + N2 (g) + 3CO2 (g) Given that 2.00 mol of gas could just expel the cannonball out of the cannon tube, what is the minimum mass of ‘black powder’ (in g), required for this to happen? [M r: KNO3, 101.1] A 101 B 135 C 202 D 270 3 Which of the following contains 1 mol of the stated particles? A electrons in 1 g of hydrogen gas B chlorine molecules in 35.5 g of chlorine gas C oxygen atoms in 22.4 dm 3 of oxygen gas at s.t.p. D hydrogen ions in 1 dm3 of 1 mol dm−3 aqueous sulfuric acid 4 The successive ionisation energies (IE) of two elements, Q and R, are given below. IE / kJ mol−1 1 st 2 nd 3 rd 4 th 5 th 6 th 7 th 8 th Q 1090 2350 4610 6220 37800 47000 - - R 1251 2298 3822 5158 6542 9362 11018 33604 What is the likely formula of the compound that is formed when Q reacts with R? A QR B Q 2R3 C QR4 D Q4R

3 5 What is th e electronic configuration of an atom of the element which is isoelectronic with H2S? A 1s2 2s2 2s6 3s2 B 1s2 2s2 2s6 3s2 3p2 C 1s2 2s2 2s6 3s2 3p4 D 1s2 2s2 2s6 3s2 3p6 6 Which of the following statements about the properties associated with ionic and covalent bonds is correct? A Some covalent compounds can serve as electrolyte in water. B Ionic bonds and covalent bonds cannot both occur in the same compound. C Ionic compounds and metals can conduct electricity in both the solid and liquid states. D Any covalent compounds that have both hydrogen and oxygen in its molecule can form intermolecular hydrogen bond. 7 Which of the following molecules will not form a hydrogen bond with another of its own molecules? A CH 3CHO C CH3OH B CH3NH2 D NH3 8 Which of the following best describes the change in the bond angle in water when the ion H 3O+ is formed? A decreases to approximately 90 B decreases to approximately 109 C increases slightly D increases to approximately 120 9 The explosive nitroglycerin (C 3H5N3O9) decomposes rapidly upon ignition or sudden impact according to the following equation: 4C3H5N3O9(l)  12CO2(g) + 10H2O(g) + 6N2(g) + O2(g) ∆Ho r = −5678 kJ mol−1 Given the following data, what is the standard enthalpy change of formation of nitroglycerin in kJ mol−1? Standard enthalpy change of formation of CO2(g) = −394 kJ mol−1 Standard enthalpy change of formation of H2O(g) = −242 kJ mol−1 A −368 C −3207 B −1470 D +5042 HCI(College) 2009 8872/01/C2 Prelim/09

4 10 What is the value of the enthalpy change for the following process equal to? Na(s)  Na+(g) + e− A the first ionisation energy of sodium B the enthalpy change of vaporisation of sodium C the sum of the first ionisation energy and the electron affinity of sodium D the sum of the enthalpy change of atomisation and the first ionisation energy of sodium 11 The bromination of propanone is acid-catalysed. CH3COCH3 + Br2 CH H 3COCH2Br + H+ + Br ─ The rate of disappearance of the bromine colour was measured for several different concentrations of propanone, bromine and H + at a certain temperature and the results tabulated below. Experiment [CH3COCH3]/ mol dm─3 [Br2]/ mol dm─3 [H+]/ mol dm─3 Rate of disappearance of Br2 colour/ mol dm─3 s─1 1 0.30 0.05 0.05 5.70 x 10─5 2 0.30 0.10 0.05 5.70 x 10─5 3 0.30 0.05 0.10 1.14 x 10─4 4 0.40 0.05 0.20 3.04 x 10─4 Which of the following statements about the above reaction is true? A The rate equation for the reaction is rate = k[CH3COCH3][Br2]. B The rate constant for the reaction is 3.8 x 10─3 mol─1 dm3 s─1. C The rate constant of the reaction doubles when [CH3COCH3] is doubled. D The rate constant of the reaction remains unchanged when temperature is doubled. 12 Two experi ments, M and N, were carried out to investigate the rates of the reaction between copper(II) carbonate and excess acid. The initial mass of the reaction vessel plus contents was the same in both experiments. The results are shown in the diagram below. Which of the following change in the conditions from Experiment M to Experiment N might explain the results shown? A increasing the concentration of the acid B increasing the mass of copper(II) carbonate C decreasing the particle size of the copper(II) carbonate D adding a catalyst Mass of reaction vessel plus contents / g Time M N Time HCI(College) 2009 8872/01/C2 Prelim/09

5 13 Phosgene, COC l2, is a poisonous gas used as a chemical weapon in World War I. It can dissociate into two other poisonous gases, carbon monoxide and chlorine, at high temperatures according to the equilibrium below: COCl 2 (g)  CO (g) + Cl2 (g) When 1 mol of phosgene is heated in a closed vessel at 600 K, the final pressure at equilibrium was 5 atm. Given that the mole ratio of phosgene to chlorine at equilibrium is 15:2, what is the numerical value of K p at 600 K? A 0.0140 B 0.0157 C 0.0702 D 0.0784 14 A solution of an acid E has the same pH as a solution of acid F. Equal dilution increases the pH of acid E more than that of acid F. Which of the following pairs of acids would show this behaviour? E F A H3PO4 HCl B HCl CH3CO2H C HCl H2SO4 D CH3CO2H H 2SO4 15 The graphs below show the variation in two properties of the elements Na to P and their compounds. Graph I Graph II Na Mg Al Si PNa Mg Al Si P Which properties are illustrated in Graphs I and II? Graph I Graph II A electrical conductivity of the element pH of the chloride when added to water B electrical conductivity of the element pH of the oxide when added to water C melting point of the element pH of the chloride when added to water D melting point of the element pH of the oxide when added to water HCI(College) 2009 8872/01/C2 Prelim/09

6 16 X, Y and Z are elements in Period 3 of the Periodic Table. A mixture containing the oxides of X, Y and Z was dissolved in excess dilute sulfuric acid and filtered. The oxide of Z was collected as a residue. When excess dilute sodium hydroxide was added to the filtrate, only a white precipitate of the hydroxide of Y was formed.