PJC H1 Chemistry 2008 JC2 H1 Chemistry Prelim Paper 1 (with answers)

PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2008 H1 CHEMISTRY 8872/01 PAPER 1 18 September 2008 50 minute s Additional materials: Data Booklet Multiple Choice Answer Sheet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Write your name, CT Group and index number on the answer sheet in the spaces provided unless this has already been done for you. There are thirty questions in this paper. Answer all questions. For each question, there are four possible answers labelled A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate 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. This document consists of 11 printed pages. [Turn Over

2 Section A For each question, there are four possible answers labelled A, B, C and D . Choose the one you consider to be correct. 1 Chlorine gas is a severe irritant to the eyes and respiratory system. The maximum safe toleration level of chlorine gas in air is 0.005 mg dm-3. How many chlorine atoms are present in 500 cm3 of air at this toleration level? A 2310 65 . 35 005 . 0 × × B 2310 6 271 1 1000 005 . 0 × × × × C 2310 62 1 71 005 . 0 × × × D 2310 671 1 1000 005 . 0 × × × 2 Bones contain a complex mixture calcium salts, protein and other material. When a bone is strongly heated in a current of air, the only residue is calcium oxide. From a sample of 50.0 g of bone, 14.0 g of calcium oxide were obtained. What is the percentage by mass of calcium in the bone? A 10.0% B 14.0% C 20.1% D 23.3% 3 To identify an oxide of nitrogen, 0.10 mol of the oxide is mixed with an excess of hydrogen and passed over a catalyst at a suitable temperature. NxOy xNH3 + yH2O H2 gas catalyst The water produced weighs 7.20 g. The ammonia produced is neutralised by 200 cm3 of 1.0 mol dm-3 HCl. What is the formula of the oxide of nitrogen? A N2O C NO2 B NO D N2O4

3 4 Gaseous particle X has proton number n and a charge of +1. Gaseous particle Y has proton number (n+1). It is isoelectronic (has the same number of electrons) with X. Which of the following statements correctly describe X and Y? A X has a larger radius than Y. B X has a greater nuclear charge than Y. C X releases more energy than Y when an electron is added to each particle D X requires more energy than Y when a further electron is removed from each particle. 5 In which of the following does ionic bonding occur between the named atoms? A aluminium and chlorine in aluminium chloride B hydrogen and sodium in sodium hydride C boron and fluorine in boron fluoride D silicon and chlorine in silicon tetrachloride 6 A solid E has the following physical properties. o It is insoluble in hydrocarbon solvents. o It melts at 1290 °C. o It conducts electricity in both aqueous and molten states. What is the likely structure of E? A an ionic structure C an atomic structure B a simple molecular structure D a giant molecular structure 7 The enthalpy change of neutralis ation of aqueous sodium hydr oxide by hydrochloric acid is -57.2 kJ mol -1, but the enthalpy change of neut ralisation of aqueous sodium hydroxide by aqueous ethanoic acid is -55.2 kJ mol-1. Which best explains the numerical difference in these values? A Aqueous ethanoic acid contains fewer hydrogen ions than hydrochloric acid of the same concentration. B The process CH3CO2H (aq) → CH3CO2 - (aq) + H+ (aq) is endothermic. C The process CH3CO2H (aq) → CH3CO2 - (aq) + H+ (aq) is exothermic. D A smaller volume of aqueous ethanoic acid is required for the neutralisation compared to that of hydrochloric acid of the same concentration.

4 8 The bond dissociation energy of H-Br is 362 kJ mol-1. Which one of the following processes will release 362 kJ of energy? A H(g) + Br (g) → HBr(g) B HBr(g) → H(g) + Br(g) C ½H2(g) + ½ Br2(g) → HBr(g) D HBr(g) → ½H2(g) + ½Br2(g) 9 Methanol is manufactured industrially by the catalytic reaction shown: CO(g) + 2H2(g) ⇌ CH3OH(g) ΔH = −92 kJmol−1 The operating conditions are 250°C, a pressure 75 atm and a copper based catalyst. Which factor influences the choice of these conditions? A The catalyst increases the equilibrium yield of methanol. B At lower pressures, the rate of formation of methanol increases. C At lower temperatures, the equilibrium yield of methanol increases. D At lower temperatures, the rate of formation of methanol increases. 10 For which equilibrium does Kc have no units? A C(s) + H2O(g) ⇌ CO(g) + H2(g) B Cu2+(aq) + 4NH3(aq) ⇌ [Cu(NH3)4]2+(aq) C N2O4(g) ⇌ 2NO2(g) D CH3OH(l) + CH3CO2H(l) ⇌ CH3CO2CH3(l) + H2O(l)

5 11 Stomach juices have a pH of 1.0. Aspirin is a monobasic acid represented by HA (K a = 10-4 mol dm-3) which dissociates into ions H+ and A-. What are the relative concentrations of H+, A- and HA when aspirin from a tablet enters the stomach? A [HA] > [H+] = [A-] B [H+] = [A-] > [HA] C [H+] > [A-] > [HA] D [H+] > [HA] > [A-] 12 One important buffer that exis ts in blood is composed of H 2PO4 -(aq) and HPO 4 2-(aq). What is the ionic equation that represents the reaction of hy drochloric acid with this buffer? A HCl(aq) + H2PO4 -(aq) → Cl-(aq) + H3PO4(aq) B H3O+(aq) + HPO4 2-(aq) → H2O(l) + H2PO4 -(aq) C H3O+(aq) + H2PO4 -(aq) → H2O(l) + H3PO4(aq) D HCl(aq) + HPO4 2-(aq) → Cl-(aq) + H2PO4 -(aq) 13 Lead is the final product formed by a series of changes in which the rate determining step is the radioactive decay of uranium-238. This radioactive decay is a first order reaction with a half life of 4.5 x 109 years. What would be the age of a rock sample, or iginally lead free, in which the molar proportion of uranium to lead is now 1:3? A 1.5 x 109 years B 2.25 x 109 years C 4.5 x 109 years D 9.0 x 109 years

6 14 It is often said that the rate of a typi cal reaction is roughly doubled by raising the temperature by 10°C. Which of the following explains this observation? A Raising the temperature by 10 °C doubles the number of molecules having energy more than a certain minimum energy. B Raising the temperature by 10°C doubles the average energy of each molecule. C Raising the temperature by 10°C doubles the average speed of each molecule. D Raising the temperature by 10 °C doubles the number of molecular collisions in a given time. 15 The ionic radius of the elements in Period 3 (Na to Cl) changes across the period. Which of the following statements does not explain the trend of the ionic radius across the period? A Across the period, there is an increase in the nuclear charge. B The anions have greater shielding effect than the cations. C There is a constant screening effect among the cations. D The effective nuclear charge decreases from P3- to Cl