Jurongville 2024 Prelim 4E Chemistry Paper 2

JVSS Prelim 2024 4E Chemistry 6092/02 [Turn over JURONGVILLE SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 Secondary 4 Express STUDENT NAME CLASS INDEX NUMBER CHEMISTRY 6092/02 Paper 2 02 August 2024 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces 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, highlighters, glue or correction fluid. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers 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 20. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A / 70 Section B / 10 Total / 80 Setter: Ms Ethel Chng This document consists of 20 printed pages.

2 JVSS Prelim 2024 4E Chemistry 6092/02 Section A Answer all questions. 1 (a) Choose from the substances listed to answer the questions. aluminium oxide calcium oxide carbon dioxide iron(II) oxide nitrogen monoxide potassium oxide sulfur dioxide Each substance may be used once, more than once or not at all. Identify the substance which (i) dissolves in water to raise the pH of soils, .……………………………………………………………………………………… [1] (ii) is a neutral oxide, .……………………………………………………………………………………… [1] (iii) reacts with both acids and alkalis, .……………………………………………………………………………………… [1] (iv) turns acidified potassium manganate(VII) from purple to colourless, .……………………………………………………………………………………… [1] (v) warms with excess hydrochloric acid to form a green solution. .……………………………………………………………………………………… [1] (b) The following are statements about alkali metals in the Periodic Table. Put a tick ( ✓) in one box in each row to show which statements are true and which are false. true false They all float on water. They lose electrons more easily down the group. They rapidly tarnish in air. They react with water to form two alkaline products. [2] [Total: 7]

3 JVSS Prelim 2024 4E Chemistry 6092/02 [Turn over 2 Magnesium, with the symbol Mg and an atomic number of 12, has a relative atomic mass of approximately 24.3. (a) Define relative atomic mass of an element. …………………………………………………………………………………………………… ……………………………………………………………………………………..………… [1] (b) The relative atomic mass of 24.3 is a weighted average of the masses of its three naturally occurring isotopes, Mg-24, Mg-25, and Mg-26. Given that the relative abundance of Mg-25 is 10%, calculate the relative abundances of Mg-24 and Mg-26. relative abundance of Mg-24 ………………………………. [1] relative abundance of Mg-26 ………………………………. [1] (c) Given that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass, comment on the relative rates of diffusion for the three Mg isotopes in the gaseous state. …………………………………………………………………………………………………… ……………………………………………………………………………………..………… [ 1]

4 JVSS Prelim 2024 4E Chemistry 6092/02 (d) Analysis of a sample of a magnesium compound shows that it contains 18.9 g of magnesium, 5.8 g of boron and 25.3 g of oxygen. Deduce the empirical formula for this magnesium compound. Show your working. empirical formula ………………………………. [ 2] (e) Admontite is a hydrated magnesium borate mineral with formula, MgB6O10•7H2O. It has an alternative formula, MgB6Ox(OH)6•yH2O. State the values of x and y in the alternative formula. x = … ……………… and y = ………………… [1] [Total: 7]

5 JVSS Prelim 2024 4E Chemistry 6092/02 [Turn over 3 Fig 3.1 shows the structures of three tetrafluorides. carbon tetrafluoride, CF4 sulfur tetrafluoride, SF4 xenon tetrafluoride, XeF4 Fig 3.1 Each of these tetrafluorides exemplifies the diversity of chemical behaviour that can arise from different central atoms bonded to fluorine. (a) Suggest how two of these structures do not follow normal bonding rules. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………..………………… [2] (b) Hydrolysis of sulfur tetrafluoride gives an intermediate product, thionyl fluoride, SOF 2. There is a double bond between atoms of sulfur and oxygen and a single bond between atoms of sulfur and fluorine. Draw a ‘dot-and-cross’ diagram to show the bonding in a molecule of SOF2. Show outer electrons only. [2] (c) Explain, in terms of structure and bonding, why these fluoride compounds have low melting points. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………..………………… [2] [Total: 6]

6 JVSS Prelim 2024 4E Chemistry 6092/02 4 The decomposition of most metal nitrates typically occurs upon heating, resulting in the formation of metal oxides, nitrogen dioxide and oxygen. (a) The thermal decomposition of calcium nitrate is considered a redox reaction. Use oxidation states to explain what is reduced and what is oxidised during the thermal decomposition of calcium nitrate. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………………..………… [2] (b) A characteristic feature of this thermal decomposition is the release of nitrogen dioxide gas. Observation of brown fumes during heating would indicate that the metal nitrate is undergoing decomposition. Describe a test to identify the other gas produced. …………………………………………………………………………………………………… ……………………………………………………………………………………..………… [ 1] (c) In an experiment, a fixed amount of three metal nitrates, calcium nitrate, lead( II) nitrate and zinc nitrate, are heated separately. (i) Assuming that the same amount of heat is applied, which metal nitrate will take the shortest time for nitrogen dioxide to appear? Explain your answer. …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... ……………………….……………………………………………………………… [2] (ii) Which solid residue is yellow when hot and turns white on cooling? ………….…………………………………………………………………………… [1] [Total: 6]

7 JVSS Prelim 2024 4E Chemistry 6092/02 [Turn over 5 Potassium nitrate is a useful water-soluble fertiliser. (a) Name the method to prepare potassium nitrate. ……………………………………………………………………………..………………… [1] (b) Write an equation, with state symbols, for the reaction to prepare potassium nitrate. ……………………………………………………………………………..………………… [ 2] (c) Describe how pure dry crystals of potassium nitrate are obtained from its aqueous solution. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………………..………… [2]

8 JVSS Prelim 2024 4E Chemistry 6092/02 (d) In an experiment, a spatula of potassium nitrate was added to 50 cm 3 of water in a beaker. The mixture was stirred to make a solution and the temper