CGSS 2023 Chemistry Prelim Paper 2A

CEDAR GIRLS’ SECONDARY SCHOOL Preliminary Examination 2023 Secondary Four CANDIDATE NAME CLASS 4 INDEX NUMBER CHEMISTRY 6092/2 Paper 2 Section A 29 August 2023 1 hour 45 minutes Additional Materials: NIL For Examiner’s Use Section A 1 5 2 11 3 7 4 12 5 7 6 8 Total 50 This document consists of 23 printed pages and 1 blank page. [Turn over READ THESE INSTRUCTIONS FIRST Write your name and index number on all the work you hand in. You may use a pencil for any diagrams, graphs or rough working. Do not use paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Write your answers in the spaces provided on the question paper. Section B Answer all three questions. The last question is in the form either/or. Write your answers in the spaces provided on the question paper. A copy of the Periodic Table is printed on page 24. At the end of the examination, hand in your answers to Section A and Section B separately.

2 For Examiner's Use 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 chlorides to answer the questions. aluminium chloride ammonium chloride calcium chloride hydrogen chloride silver chloride sodium chloride Each chloride may be used once, more than once or not at all. Which chloride (a) contains a cation with a +2 charge ………………………………………..……………………………………………… [1] (b) reacts with warm aqueous sodium hydroxide to form a gas which turns damp red litmus paper blue ………………………………………..……………………………………………… [1] (c) has a molecule which only has 18 protons ………………………………………..……………………………………………… [1] (d) forms a white precipitate in aqueous ammonia ………………………………………..……………………………………………… [1] (e) is soluble in organic solvents? ………………………………………..……………………………………………… [1] [Total:5]

3 [Turn over For Examiner's Use A2 Hydrogen is used as an alternative energy source as it is a clean fuel. The process of making hydrogen has several stages. The equations show two stages in the process. Stage 1: CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g) Stage 2: CO(g) + H2O(g) ⇌ CO2(g) + H2(g) (a) Both stages require the use of catalyst s to increase the rate of reaction. Catalysts are expensive to buy but reduce costs in the long run. (i) Explain, in terms of collisions and energy, why using a catalyst increases the rate of reaction. ………………………………………………………………………………….. ………………………………………………………………………………….. ………………………………………………………………………………….. ………………………………………………………………………………….. ………………………………………………………………………………….. [2] (ii) Give two reasons to explain why catalysts reduce costs in the long run. ……………………………………………