2022 NYGH Chem Prelims P2

Class Centre/Index Number Name Preliminary Examination 2022 Secondary 4 CHEMISTRY Paper 2 6092/02 1 hour 45 minutes Friday 26 August 0845 – 1030 No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, register number and class in the spaces at the top of this page. Write in dark blue or black pen. You may use a pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid / tape. Section A (50 marks) Answer all questions in the spaces provided. Section B (30 marks) Answer all three questions, the last question is in the form either/or. Indicate in the box to the right your choice of the either/or question. 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 23. The use of an approved scientific calculator is expected, where appropriate. Examiner’s Use Paper 1 Paper 2 Indicate the question attempted for B9 with a tick (). Either  Or  Total This document consists of 23 printed pages and 1 blank page. Setter: FKD NANYANG GIRLS' HIGH SCHOOL [Turn over

2 Section A Answer all questions. Write your answers in the spaces provided on the question paper. A1 Choose from the following substances to answer the questions below. Each of these substances can be used once, more than once or not at all. Al2O3 Ar CaO CH4 CO2 Ba(NO3)2 TiO2 Pb(NO3)2 (a) Which substance forms approximately 1 % of clean, dry air? [1] (b) Which substance is the main constituent of natural gas? [1] (c) Which substance dissolves in water to form an aqueous solution which gives a white precipitate on addition of aqueous sodium chloride? [1] (d) Which substance reacts with both acids and alkalis? [1] (e) Which substance is most likely to be coloured and can be used as a catalyst? [1] (f) Which two substances are the products of thermal decomposition of limestone? [1] [Total: 6]

3 [Turn over A2 A student sets up a tube as shown in the diagram. Concentrated hydrobromic acid produces fumes of hydrogen bromide. Concentrated aqueous ammonia produces fumes of ammonia. After sometime, solid ammonium bromide appeared on the walls of the tubes. (a) (i) Calculate the relative molecular mass of hydrogen bromide and ammonia. [1] (ii) Hence, state the position ( A, B or C) of where the solid ammonium bromide may appear in the tube above. [1] (iii) Explain your answer to (a)(ii). [2] (b) Draw a ‘dot-and-cross’ diagram for ammonia. Show only the outer electrons. [2] A B C

4 (c) Explain why ammonium bromide exists as a solid at room temperature and pressure.