2022 SCGS Chem Prelims P2

CANDIDATE NAME CLASS 4 REGISTER NUMBER CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 2 Theory 6092/02 23 August 2022 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your class, index number and name on all the work you hand in. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. 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 printed on page 21. The use of an approved scientific calculator is expected, where appropriate. This question paper consists of 21 printed pages and 1 blank page. SINGAPORE CHINESE GIRLS’ SCHOOL Preliminary Examination Secondary Four For Examiner’s Use Section A 50 Section B 30 Total 80

2 {Turn Over Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. A1 Use the substances in the list below to answer the following questions. Each option may be used once, more than once or not at all. aluminium iodide sodium chloride ammonium chloride zinc chlorine nitric acid sodium bromide potassium carbonate (a) Which substance in aqueous form reacts with aqueous chlorine to form a brown solution with black crystals? ………………………………………………………………………………………………... [1] (b) Which substance can reduce hydrochloric acid in a redox reaction? ………………………………………………………………………………………………... [1] (c) Which substance , when warmed in a mixture with aqueous sodium hydroxide and aluminium, produces a gas that turns moist litmus blue? ………………………………………………………………………………………………... [1] (d) Which substance produces a reddish brown vapour when it conducts electricity in the molten state? ………………………………………………………………………………………………... [1] (e) Which salt cannot be prepared by titration method? ………………………………………………………………………………………………... [1] [Total 5] A2 The table below lists some information about the elements in Period 3 in the Periodic Table. Element Na Mg Al Si P S Cl Ar Number of valence electrons 1 2 3 4 5 6 7 8 Common oxidation state +1 +2 +3 +4 / - 4 -3 -2 -1 0 Melting point /oC 98 650 660 1414 317 115 -101 -189 (a) Explain the variation in oxidation state(s) across the period. ...…………………………………………………………………………………………………. ...…………………………………………………………………………………………………. ...…………………………………………………………………………………………………. .…………………………………………………………………………………………………... [2]

3 [Turn Over (b) Explain the large difference in melting points between silicon and chlorine. ...…………………………………………………………………………………………………. ...…………………………………………………………………………………………………. ...……