2013 TPJC H1 Chemistry P1 Suggested Solution

TPJC_2013_8872_01 [Turn over READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write your name and civics group on the Answer Sheet in the spaces provided. There are thirty 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 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 on this paper. This document consists of 13 printed pages and 1 blank page. TAMPINES JUNIOR COLLEGE JC2 Preliminary Examination CANDIDATE NAME TUTOR NAME 1 2 CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 8872/01 Monday, 23 September 2013 50 minutes H1 CIVICS GROUP

2 TPJC_2013_8872_01 Section A For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1 Use of the Data Booklet is relevant to this question. How many molecules are present in 1 cm3 of oxygen gas under room conditions? A 231002.6 240001 × × B 24000 1002.61 23×× C 10001 240001002.6 23 × ×× D 321002.61 23××× 2 Which of the following ions would undergo the greatest deflection in an electric field? A 16O2+ B 16O18O+ C 16O18O2+ D 18O2+ 3 10 cm3 of 0.2 mol dm−3 K2XO4 will just react with 40 cm3 of 0.1 mol dm−3 iron(II) sulfate solution. If Fe2+ is oxidized to Fe3+ by K2XO4, what is the final oxidation state of X? A +2 B +3 C +4 D +5 4 The table gives the successive ionisation energies for an element X. 1st 2nd 3rd 4th 5th 6th Ionisation energy/ kJ mol−1 950 1800 2700 4800 6000 12300 What could be the formula of the chloride of X? A XCl B XCl2 C XCl3 D XCl4

3 TPJC_2013_8872_01 [Turn over 5 Which of the following consists of species which are all planar? A CO32– , SO32– and benzene B Al2Cl6 , SOCl2 and methanal C NO3– , XeF4 and ethanal D BCl3 , ICl4− and chlorobenzene 6 Dot-and-cross diagrams for carbon monoxide are shown. Which circled pair of electrons represents a coordinate bond? A B C D 7 The diagram shows the Boltzmann distribution of the speeds of the molecules of a gas. Point X represents the most probable speed. If the gas is cooled, in which direction does X move? A 8 Iodine-131 is a radioactive isotope with a half-life of 8 days. Given that radioactive decay is a first-order reaction, what fraction of the isotope would remain after 80 days? A 20 1 B 160 1 C 82 1 D 102 1

4 TPJC_2013_8872_01 9 The table shows the charge and radius of each of six ions. ion J+ L+ M2+ X− Y− Z2− radius/ nm 0.14 0.18 0.15 0.14 0.18 0.15 The ionic solids JX, LY, and MZ have the same lattice type. What is the order of their lattice energies starting from the most exothermic first? A JX, MZ, LY B LY, MZ, JX C MZ, JX, LY D MZ, LY, JX 10 Dinitrogen oxide, N=N=O, burns in ethyne, C2H2, in the gaseous phase to produce water vapour, carbon dioxide and nitrogen gases as the only products. 5N2O(g) + C2H2(g) → H2O(g) + 2CO2(g) + 5N2(g) ΔH = −1668 kJ mol−1 Assuming N=N bond energy in dinitrogen oxide is +418 kJ mol−1, what is the nitrogen-oxygen bond energy in dinitrogen oxide in kJ mol−1? A 382 B 594 C 686 D 1350 11 Which is the correct statement about the following reaction? P(g) + Q(g) R(g) ∆H < 0 A The solid M will lower the activation energy of both forward and backward reactions. B Both the rate constant and equilibrium constant will increase with increasing temperature. C Increasing temperature will lower the activation energy resulting only in a greater fraction of R molecules with energy greater than activation energy. D The activation energy of the forward reaction is equal to the activation energy of the backward reaction. 12 Phosphorus is an element in the third period, Na to Ar, of the Periodic Table. What is true for phosphorus and none of the other elements in this period? A Phosphorus has the highest melting point of the elements in this period. B Phosphorus is the only element in this period that forms two acidic oxides. C Phosphorus is the only element in this period with exactly four atoms in its molecule. D Phosphorus is the only element in this period whose chlorides react with water to form acidic solutions. M(s)

5 TPJC_2013_8872_01 [Turn over 13 The bar chart shows the melting points of a series of consecutive elements arranged in order of increasing atomic number. The elements sodium to chlorine form part of this series. Which bar represents sodium? B 14 The chloride of element Q is hydrolysed by water to form an acidic solution and its oxide reacts with acid to form a salt. What could be element Q? A sodium B aluminium C silicon D phosphorus

6 TPJC_2013_8872_01 15 The reaction between NO and F2 was studied by mixing the two gases: 2NO(g) + F2(g) 2NOF(g) ΔH < 0 At different times during the experiment, various changes were made to the conditions inside the reaction vessel. The changes in concentrations of the three compounds in the equilibrium mixture with time are given by the graph below: Which of the following statements is correct? A There was a decrease in volume of the reaction vessel at 10.0 min. B There was an increase in volume of the reaction vessel at 7.5 min. C There was an increase in temperature at 10.0 min. D A catalyst was added at 7.5 min. 16 A solution of pH 1.3 was produced when 0.10 mol of an acid, U, was dissolved in 2 dm3 of water. Given the above information, which of the following statements is true? A The solution contains 0.050 mol of hydrogen ions. B U is a weak acid with a large Ka value. C U is a diprotic strong acid. D U is a monoprotic strong acid.

7 TPJC_2013_8872_01 [Turn over 17 The graph shows the change in pH when ethanoic acid is gradually added to 10 cm3 of 0.10 mol dm−3 sodium hydroxide. An indicator is used to determine the end-point for the titration. Which of the following contains the correct concentration of ethanoic acid and indicator used for the titration? A 0.05 mol dm−3 ethanoic acid, phenolphthalein B 0.05 mol dm−3 ethanoic acid, screened methyl orange C 0.10 mol dm−3 ethanoic acid, phenolphthalein D 0.10 mol dm−3 ethanoic acid, screened methyl orange 18 What is meant by the term dynamic equilibrium? A An equilibrium that is constantly changing its position. B An equilibrium where the forward and reverse reactions are taking place at different rates. C An equilibrium where the forward and reverse reactions are taking place at the same rate. D An equilibrium which has not yet settled to a constant state.

8 TPJC_2013_8872_01 19 Dibenzalacetone is a bright yellow solid with the following structure. O dibenzalacetone How many geometric isomers does dibenzalacetone have? A 2 B 3 C 4 D 5 20 A food chemist wants to create the odour of green apples for a product. An ester with this odour has the formula C2H5CO2CH(CH3)2. In which of the following will the substances react together to produce this ester? A C2H5OH and (CH3)2CHCOOH B CH3COOH and CH3CH(OH)CH2CH3 C C2H5COOH and C2H5CH2OH D C2H5COOH and (CH3)2CHOH 21 Which is not a possible product formed when the following compound is heated with excess ethanolic KOH? Br Br Br A C B D

9 TPJC_2013_8872_01 [Turn over 22 2,4–D and MCPA are two common selective weed killers. Which one of the following reagents can be used to distinguish between them? A sodium metal B phosphorus pentachloride C 2,4-dinitrophenylhydrazine D hot acidified potassium dichromate(VI) 23 Deuterium, D, is an isot