2022 YYSS Chem Prelims P2

YUYING SECONDARY SCHOOL PRELIMINARY EXAMINATION Secondary 4 Express NAME CLASS REG. NO CHEMISTRY 6092/2 Paper 2 25 August 2022 1 hour 45 minutes Candidates answer on the Question Paper. Additional Materials: Nil Setter: Mr Danny Louis READ THESE INSTRUCTIONS FIRST Write your name, class and register number on this question booklet. Write in dark blue or black pen on both sides of the paper. You may use a pencil for any diagrams, graphs, tables or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer all the questions in this section in the spaces provided. The last question is in the form either/or and only one of the alternatives should be attempted. Write your answers in the spaces provided on the Question Paper. The use of an approved calculator is expected, where appropriate. 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 19. For Examiner’s Use Total This document consists of 19 printed pages. 80

2 Section A Answer all the questions in this section in the spaces provided. The total mark for this section is 50. A1 A list of gases is given below. A CO B NO C CH4 D SO2 E NH3 F CO2 Use the letters A, B, C, D, E and F to answer the following questions. Each letter may be used once, more than once or not at all. [ 5 ] (a) Which gas can be formed by lightning activity in the atmosphere? ___________ (b) Which is the lightest gas? ___________ (c) Which gas is formed by the decay of organic matter? ___________ (d) Which gas is used to reduce iron(III) oxide in the blast furnace? ___________ (e) Which gas turns damp red litmus paper blue? ___________ A2 A block of magnesium is burnt in oxygen to form magnesium oxide. Complete the diagrams below to show the arrangement of particles before and after the reaction. magnesium magnesium oxide [ 2 ] key oxygen atom magnesium atom

3 A3 The triple point of a pure substance is the temperature at which the substance can exist as a solid, liquid and gas at the same time. The figure below shows the triple point of carbon dioxide. (a) Mark the triple point of carbon dioxide on the figure with an ‘X’. [ 1 ] (b) A student is given carbon dioxide gas at room conditions (25 oC and 1 atm). Suggest how liquid carbon dioxide can be obtained by changing one of the conditions. [ 1 ] ___________________________________________________________ (c) Draw a ‘dot-and-cross’ diagram to show the electrons in a molecule of carbon dioxide. Show only the valence electrons in your diagram. [ 2 ] (d) What type of oxide is carbon dioxide? State one property you would expect this oxide to have. [ 2 ] ___________________________________________________________ ___________________________________________________________ pressure / atm temperature / oC

4 A4 A sample of ink contains a mixture of red, blue and yellow dyes. To separate the dyes in the ink, the solvent used is a mixture of water and ethanol. The Rf values of the coloured dyes in solvents with different percentage of ethanol by volume in water are shown in the graph below. Use the information above to answer the following questions. (a) Explain why a pure solvent of either water or ethanol cannot be used to identify the dyes in the ink. [ 2 ] ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ (b) A mixture of water and ethanol was used to separate a sample of this ink. Only one spot was formed on the chromatogram. Explain why it cannot be concluded that the ink sample is a pure substance. [ 1 ] ___________________________________________________________ ___________________________________________________________ (c) What is the Rf value of the blue, red and yellow dye when a solvent mixture containing 90 cm3 ethanol and 60 cm3 water is used in the chromatography? [ 2 ] blue: ___________ red: ___________ yellow: ___________ A5 Boron is in Group III of the Periodic Table and exhibits the properties of a non-metal. It reacts with nitrogen to form boron nitride. One form of boron nitride is Percentage of ethanol in water Rf value

5 the hexagonal form which has a structure similar to graphite as shown in the figure below. Unlike graphite, hexagonal boron nitride does not conduct electricity. (a) Explain why hexagonal boron nitride is unable to conduct electricity. [ 2 ] ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ (b) Hexagonal boron nitride is used in the making of lipsticks. Explain, in terms of the structure and bonding in hexagonal boron nitride, why it is suitable as the material for making lipsticks. [ 2 ] ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ (c) How would you expect the melting point of hexagonal boron nitride to be like? [ 1 ] ___________________________________________________________ A6 Copper can react with either chlorine or bromine to form copper(II) halide. Key: boron nitrogen

6 Cu + Cl2 → CuCl2 Cu + Br2 → CuBr2 (a) Which statement(s) about the formation of copper(II) halide is/are true and which is/are false? Put a tick () in one box in each row. true false The formation of copper(II) chloride is faster than that of copper(II) bromide. The number of electron shells of the halide increase by one after copper(II) halide is formed. The reactions are redox in nature. [ 3 ] (b) Describe how a pure and dry sample of copper can be separated from a solid mixture containing copper(II) halide and copper. [ 2 ] ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ (c) 96 g of copper metal reacted with an excess of chlorine gas. What is the mass of copper(II) chloride formed? [ 2 ] A7 The set-up below is used to determine the order of reactivity of five metals; copper, P, Q, R and S. wire

7 The results are summarised in the table below. metal strip direction of electron flow voltage / V P from P to copper 0.52 Q from copper to Q 0.33 R from R to copper 1.51 S from S to copper 1.25 (a) Arrange the five metals in order of increasing reactivity. [ 1 ] ___________________________________________________________ (b) Given that metal S is from Group II, give two observations that will be seen when a piece of metal S is dipped in a solution of copper(II) sulfate. [ 2 ] 1. _________________________________________________________ 2. _________________________________________________________ (c) When a zinc strip is used with the copper