2022 JYSS Chem Prelims P2

CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER CHEMISTRY 6092/02 Paper 2 26 August 2022 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, index number 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. 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. A copy of the Periodic Table is printed on page 24. The use of an approved scientific calculator is expected, where appropriate. This document consists of 23 printed pages and 1 blank page. General Certificate of Education Ordinary Level JUYING SECONDARY SCHOOL, SINGAPORE Secondary Four Express Preliminary Examination

2 Section A Answer all the questions in this section in the spaces provided. The total mark for this section is 50. A1 (a) Fig. 1.1 shows part of the Periodic Table. Fig. 1.1 Answer the questions using only the symbols of the elements in Fig. 1.1. Each symbol may be used once, more than once or not at all. State the symbol of an element that: (i) is a monoatomic gas at room temperature; …………………………………………………………………………….……. [1] (ii) is used to test for unsaturated hydrocarbons; …………………………………………………………………………….……. [1] (iii) displaces bromine from its halide; …………………………………………………………………………….……. [1] (iv) has 24 protons in each atom; …………………………………………………………………………….……. [1] (v) forms an amphoteric oxide. …………………………………………………………………………….……. [1] I II III IV V VI VIII VII H Mg K Ca Cr Fe Cu Zn Al Cl N O Ne Br I

3 (b) An atom has the electronic configuration 2, 8, 4. State which period and group the atom belongs to in the Periodic Table. ……………………………………………………………………………………..….. [1] (c) To find out the nucleon number of a Cl atom, a student checks the Periodic Table and records the nucleon number as 35.5. Explain why the student is incorrect and what should be done instead. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2] [Total: 8]

4 A2 Fig. 2.1 shows an electrolytic cell. The terminals of the battery are labelled as 1 and 2, while the graphite electrodes are labelled as X and Y. A few drops of Universal Indicator are added to the electrolyte. Fig. 2.1 (a) When the experiment begins , colourless gas es are observed to form at both electrodes. Table 2.2 shows the results of the gas tests performed. Table 2.2 test gas at electrode X gas at electrode Y lighted splint extinguishes with ‘pop’ burns strongly glowing splint extinguishes relights (i) Explain which terminal, 1 or 2, acts as the negative terminal of the battery. ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………….. [2] (ii) Write the ionic half-equation for the reaction at electrode Y. ………………………………………………………………………………….. [1] 1 2 electrode Y electrode X clamp U-tube aqueous sodium chloride with Universal Indicator

5 (b) At the start of the experiment , the Universal Indicator in the U-tube is green in colour. As the experiment progresses, the solution at electrodes X and Y on each end of the U-tube turns to a different colour. (i) State the colour observed at electrode X. ……………………………………………………………………………..…… [1] (ii) Explain why at electrode Y the indicator turns red initially but is then bleached to colourless after some time. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………….. [3] (c) In another experiment, some changes are made to the set-up in Fig. 2.1.  The battery is removed and replaced with a lamp.  The electrolyte is replaced with silver nitrate solution without adding any indicator.  Electrode X is replaced with copper and electrode Y is replaced with silver. (i) Explain why the lamp is observed to light up. ……………………………………………………………………………………… ………………………………………………………………………………….. [1] (ii) Describe two observations that would be seen after some time. ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………….. [2] [Total: 10]

6 A3 Solutions of iron(II) chloride and iron(III) chloride are added separately to solutions of potassium iodide and acidified potassium manganate. (a) Complete Table 3.1 to show the colour changes to potassium iodide and acidified potassium manganate. Table 3.1 iron(II) chloride solution iron(III) chloride solution potassium iodide solution no change to potassium iodide acidified potassium manganate solution no change to potassium manganate [2] (b) One of the reactions in Table 3.1 can be represented by the ionic equation shown. MnO4–(aq) + 8H+(aq) + 5Fe2+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) Use oxidation states to explain why this is a redox reaction. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2] (c) Describe a different chemical reaction to distinguish between solutions of iron(II) chloride and iron(III) chloride. In your answer, include the observations to be made for each solution, and an ionic equation for any one of the reactions. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [3] [Total: 7]

7 A4 (a) Sulfamic acid, H2NSO3H, is a strong acid frequently used for the removal of rust from iron structures. (i) A 0.105 g sample of sulfamic acid is dissolved in water to form a solution. The solution requires 10.8 cm 3 of 0.100 mol/dm 3 aqueous potassium hydroxide for complete neutralisation. Calculate the number of moles of sulfamic acid that react with one mole of potassium hydroxide. [3] (ii) State the conditions required for rust to form on iron structures. ..………………………………………………………………………………… [1]

8 (b) Methylamine, CH3NH2, is a weak base. (i) A sample of methylamine is added to water. CH3NH2 + H2O ⇌ CH3NH3+ + OH– Predict the pH of aqueous methylamine and explain your answer. ……………………………………………………………………………………… ………………………………………………………………………………….. [2] (ii) Methylamine can neutralise acids such as dilute hydrochloric acid, to form the salt methylammonium chloride. CH3NH2 + HCl → CH3NH3Cl Hence, write a balanced equation for the reaction between methylamine and sulfuric acid, and suggest the name of the salt formed. ……………………………………………………………………………………… ……………………………………………………………………………….….. [2] [Total: 8]

9 A5 (a) An experiment is conducted to investigate the thermal stability of the carbonates of four different metals, P, Q, R and S. The metal carbonates are heated strongly and the volume s of carbon dioxide gas produced in the first 5 minutes are recorded in Table 5.1. Table 5.1 carbonate of metal time (min) 1 2 3 4 5 P volume of carbon dioxide (cm3) 5 11 16 21 27 Q 3 6 9 12 15 R 0 0 0 0 0 S 8 16 24 32 40 (i) Explain which metal carbonate has the lowest thermal stability. .……...………………………………………………………………………..……. ......……………………………………………………………………………… [1] (ii) Table 5.2 shows information about the ions of metals P, Q, R and S. The charge density is the r