NJC 2018 SH1 H1 Promo Paper 2 Question

1 NJC Promotional Examination 887302/18 [Turn over SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 2 Structured Questions Additional Materials: Data Booklet Writing Papers 8873/02 Mon 1 October 2018 1.5 hours READ THE INSTRUCTIONS FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use paper clips, highlighters, glue or correction fluid. Answer all questions in Section A (40 marks) in the space provided on the Question paper. Answer one question in Section B (20 marks) on the writing paper provided separately. The use of an approved calculator is expected, where appropriate. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Appropriate significant figures and units are expected for final numerical answers For Examiner’s Use 1 / 8 2 / 7 3 / 7 4 / 9 5 / 9 6 /20 Paper 2 / 60 Paper 1 / 20 Overall Total / 80 Overall percentage / 100 This document consists of 10 printed pages. NATIONAL JUNIOR COLLEGE SH1 PROMOTIONAL EXAMINATION Higher 1 CANDIDATE NAME

2 NJC Promotional Examination 8873/02/18 Answer ALL questions in the spaces provided. 1 (a) The element nickel was discovered in 1751 by Swedish chemist A. F. Cronstedt. (i) Nickel is a transition metal. Describe the bonding in the element nickel. You should draw a labelled diagram to illustrate your answer. [2] (ii) State two physical properties that you would expect nickel metal to possess. Explain, in terms of the bonding present, why it possesses these properties. property ………………………………………………………………………………. Explanation …………………………………………………………………………… …………………………………………………………………………………………... …………………………………………………………………………………………... property ………………………………………………………………………………. explanation …………………………………………………………………………… …………………………………………………………………………………………... …………………………………………………………………………………………... [3] (b) A common battery is the nickel -cadmium cell. It has one electrode of cadmium and one electrode of nickel ( III) hydroxide, Ni(OH) 3. The two electrodes are connected using an electrolyte. The two half-equations for this cell are: Cd(OH)2 + 2e− Cd + 2OH− Ni(OH)3 + e− Ni(OH)2 + OH− (i) Combine these two half-equations to show the above overall reaction. ………………………………………………………………………………………...[1]

3 NJC Promotional Examination 8873/02/18 [Turn over 1 (b) (ii) Using your equation in (b)(i), identify the species that have been reduced and oxidised respectively. Species reduced: …………………………… Species oxidised: …………………………… [2] [Total: 8] 2 Sulfur is a common element on Earth that forms many important chemical compounds. The table below shows the melting point of sulfur and some of its compounds. Compound Melting point / °C Sulfur, S8 115 Sodium thiosulfate, Na2S2O3 49 Sodium sulfide, Na2S 117 (a) Draw the dot-and-cross diagram of sodium sulfide, Na2S. [2] (b) By considering the bonding and structure, explain why sulfur has a higher melting point than sodium thiosulfate. (i) …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... ………………………………………………………………………………………...[3]

4 NJC Promotional Examination 8873/02/18 2 (b) (ii) How would you expect the magnitude of the lattice energy of Na 2S to compare with that of Na2S2O3? Explain your answer. …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... ………………………………………………………………………………………...[2] [Total: 7] 3 The following reaction scheme shows how compound A, CH3CHClCH2CH3 could be formed and converted to other useful organic products. (a) Give the name for compound A. ………………………………………………………. [1] (b) Suggest the reagents and conditions for step I and II. ………………………………………………………………………………….……….………. ……………………………………………………………………………………….……….[2] (c) Suggest the type of reaction for step II. ………………………………………………………………………………………………..[1] (d) Write a balanced equation for the reaction B with hydrogen. ………………………………………………………………………………………………..[1] (e) Compound B exhibits cis-trans isomerism. Draw and name the isomers. [2] [Total: 7] CH3CH2CH2CH3 CH3CHClCH2CH3 I CH3CH=CHCH3 A B II

5 NJC Promotional Examination 8873/02/18 [Turn over 4 Nitrogen monoxide reacts with oxygen gas according to the equation: 2NO(g) + O2(g) → 2NO2(g) An experiment is performed to determine the order of reaction with respect to nitrogen monoxide and oxygen. The concentration of oxygen used for both experiments is 0.005 mol dm−3. The results are as follows. (a) Using the graphs above, determine the order of reaction with respect to O2 and NO, showing your workings clearly. [2] (b) Write a rate equation for the reaction. ……………………………………………………………………………………………..…[1]

6 NJC Promotional Examination 8873/02/18 4 (c) Calculate the initial rate of reaction for Experiment 1. Hence, calculate the rate constant, including its units. [3] (d) With the aid of a Maxwell-Boltzmann distribution curve, explain how the rate of reaction will be affected if the reaction was carried out at a higher temperature. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……...………………………………………………………………………………………...[3] [Total: 9]

7 NJC Promotional Examination 8873/02/18 [Turn over 5 Instant cold packs are convenient replacements for ice used as first aid on injuries. They usually consist of two bags; an inner bag containing water placed inside a bag containing an ionic salt. When the instant cold pack is squeezed hard enough, the bag containing the water breaks. The ionic salt dissolves in the water in an endothermic process. For the instant ice pack to be effective, the overall temperature of the cold pack must decrease by at least 7.00 °C. Company Z has been researching on the cost effectiveness of using either solid ammonium nitrate, NH4NO3, or solid ammonium chloride, NH4Cl, as the ionic salt in its instant cold packs containing 100 cm 3 of water. It has been found that 25.4 kJ of energy is absorbed when 1 mol of solid NH 4NO3 is fully dissolved in water at standard conditions according to the following reaction. NH4NO3(s) → NH4+(aq) + NO3−(aq) The prices and molar masses of both ionic salts are listed in the table below. Ionic Salt Molar mass / g mol-1 Cost of 1000 g of salt /