2022 WSSS Chem Prelims P2

West Spring Secondary School Preliminary Examination 2022 CHEMISTRY Paper 2 6092/02 SECONDARY 4 EXPRESS Name ( ) Date 26 August 2022 Class Duration 1 hour 45 minutes Additional materials: Laminated Periodic Table READ THESE INSTRUCTIONS FIRST Write your index number, class and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided. Section B Answer all three questions, the last question is in the form either/or. Answer all questions in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is provided separately. The use of an approved scientific calculator is expected, where appropriate. FOR EXAMINER’S USE Section A / 50 Section B / 30 Total / 80 This document consists of 20 printed pages including the cover page. Setter: Mdm Sharena [Turn over The image part with relationship ID rId9 was not found in the file.

2 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. A1 Choose from the following reactions/processes to fill in the blanks. Each reaction/process may be used once, more than once or not at all. Precipitation Displacement Reduction Decomposition Neutralisation Combustion Oxidation Dissociation (a) When potassium hydroxide and carbonic acid reacts, … ……………………………. . occurs. [1] (b) Iron undergoes ………………………………... during rusting. [1] (c) Copper(II) carbonate undergoes ……………………………….. to form copper(II) oxide and carbon dioxide. [1] (d) Copper(II) oxide can undergo ……………………………….. to form copper, by reacting with hydrogen. [1] (e) Methane undergoes ……………………………….. when it reacts with air to produce carbon dioxide and water vapour. [1] [Total: 5] A2 Chromatography can be used to separate components of a mixture. A student used paper chromatography to analyse a black food colouring. The student placed spots of known food colours, A, B, C, D and E, and the black food colouring on a sheet of chromatography paper and carried out paper chromatography using ethanol as the solvent. The results are shown on the chromatogram in Figure 2.1. Fig. 2.1 A B C D E solvent front start line black food colouring

3 (a) Which of the known food colours is insoluble in ethanol? …………………………. [1] (b) What does the chromatogram tell you about the composition of the black food colouring? ……………………………………………………………………………………………………………. …………………………………………………………………………………………..……………..[2] (c) Table 2.1 gives the results of chromatography experiments that were carried out on some known food colours, using ethanol as the solvent. Table 2.1 name of food colour distance from start line to solvent front in mm distance moved by food colour in mm Rf value Ponceau 4R 62 59 0.95 Carmoisine 74 45 0.61 Fast red 67 27 0.40 Erythrosine 58 17 0.29 Using Figure 2.1 and the information in Table 2.1, calculate the R f value of food colour C to determine which of the food colours in the table could be food colour C? Use the formula, Food colour C is ………………………………………….. [2] Rf value = distance travelled by food colour C distance travelled by the solvent [Total: 5]

4 A3 An experiment was set up to investigate the movement of gaseous ammonia and gaseous hydrogen chloride. (a) The white powder forms on the tube due to the reaction between gaseous ammonia and gaseous hydrogen chloride to produce solid ammonium chloride. Insert the correct symbol in the equation to show that this reaction is reversible. NH3 + HCl NH4Cl [1] (b) The tube contains two pieces of Universal Indicator paper. Complete Table 3.1 to show the colours and pH values of each piece of paper at the end of the experiment. Table 3.1 Universal Indicator paper colour pH 1 2 [2] (c) Explain why the white powder does not form at the centre of the tube. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………..[3] [Total: 6] cotton wool soaked in concentrated ammonia solution damp universal indicator paper 1 damp universal indicator paper 2 cotton wool soaked in concentrated hydrochloric acid white powder forms on tube here

5 A4 Strontium-88 has three other isotopes. Figure 4.1 is the mass spectrum that shows the relative abundance of each isotope. Fig. 4.1 (a) Calculate the relative atomic mass of strontium. Show your working clearly. [2] (b) 180 g of strontium-88 burns in oxygen to form 245 g of strontium peroxide. Show that the empirical formula of strontium peroxide is SrO2. [2] mass spectrum of strontium 90 80 70 60 50 40 30 20 10 0 relative abundance (%) mass number of isotopes 84 86 87 88

6 (c) The reaction between strontium and oxygen is a redox reaction. Sr + O2 → SrO2 Oxygen acts as an oxidising agent in the reaction. Use ideas about oxidation state to explain that the statement is true. ……………………………………………………………………………………………………………. ……………………………………………………………………………………………………………. ………………………………………………………………………………………………………….[2] (d) Strontium also forms strontium superoxide, Sr(O2)2, with oxygen. Determine the formula for a superoxide ion. ………………………………………………………………………. ……………………… .…………[1] [Total: 7] A5 Astatine, At, is an element in Group VII of the Periodic Table. It exists as diatomic molecules similar to the other elements in the same Group. Two isotopes of astatine are known to exist : astatine-210 and astatine-211. It reacts with calcium (Ca) to form the compound calcium astatide. symbol number of protons number of neutrons number of electrons At210 85 At211 85 (a) Complete the table above. [2] (b) Using astatine-210 and astatine-211 as examples, describe one similarity and one difference in terms of the particles in their nucleus. ………………………………………………………………………………………………… ..………… …………………………………………………………………………………………………… ..……… ……………………………………………………………………………………………………… ..…[ 2]

7 (c) Draw the ‘dot-and-cross’ diagram for astatine. Show outer electrons only. [1] (d)