Whitley Prelim P2

Name: ( ) Class: WHITLEY SECONDARY SCHOOL A Caring and Learning Community of Leaders Perseverance * Respect * Integrity * Discipline * Empathy PRELIMINARY EXAMINATION 2024 READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, 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. 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. This paper consists of 20 printed pages. SUBJECT : Chemistry (6092/02) LEVEL : Secondary 4 Express DATE : 20 August 2024 DURATION : 1 hour 45 minutes SETTER : Mrs Ambikai VETTERS : Ms Charlene Lye and Mr Ng Mun Leong For Examiner’s Use Section A /70 Section B /10 Total /80

2 Section A Answer all questions. 1 Table 1.1 below shows a list of elements and their atomic and mass numbers. Table 1.1 element A B C D E F G H atomic Number 8 12 16 17 18 28 31 35 mass Number 16 24 32 37 40 59 70 80 Using only the elements from Table 1.1, choose an element which matches the following descriptions. Each element can only be used once. (a) (b) (c) (d) (e) Forms coloured compounds. …………………………………………………………………………...……………............ [1] Forms an oxide that reacts with acids only. ……....………………………………………………………………...……...………………... [1] Forms an anion with a charge of -2 most readily. ……..…………………………………………………………………………………………… [1] Could be an isotope of chlorine-35. ………………………………………………………………………………………………….. [1] A gas used to fill up light bulbs. ………………………………………………………………………………………………….. [1] [Total: 5]

3 2 Fig. 2.1 describes reactions involving a pale green solid, A. Fig. 2.1 (a) Name A, B, C and D. A ………………………………………………………… B ………………………………………………………… C ………………………………………………………… D ………………………………………………………… [4] (b) Write the ionic equation for the reaction between B and acid D. ...................................................................................................................................... [1] (c) Explain why precipitate F changed to form reddish brown precipitate H when left to stand for a few minutes. ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [1] [Total: 6]

4 3 The diagram in Fig. 3.1 shows the formation of boron trifluoride. Only valence electrons are shown in the diagram. Fig. 3.1 (a) Using the information from the above diagram, explain if you would classify boron as a metal or non-metal. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [1] (b) State what is unusual about the bonding in boron trifluoride. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [2] (c) Using your knowledge of chemical bonding, predict whether the melting point of boron trifluoride will be generally high or low. Explain your answer. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [2] [Total: 5]

5 4 Vanadium and manganese are metals which can form variable oxidation states and compounds of different colours. (a) Table 4.1 shows the colours of vanadium in different oxidation states. Complete the oxidation states of vanadium in the table. Table 4.1 substance colour oxidation state of Vanadium [V(H2O)6]3+ green [VO2]+ yellow [V(H2O)6]2+ violet [VO]2+ blue [2] (b) Manganese nitrate, Mn(NO3)2, decomposes upon strong heating to form manganese oxide, MnO2, and nitrogen dioxide gas. (i) Write a balanced chemical equation for the decomposition of manganese nitrate. .............................................................................................................................. [1] (ii) Is the decomposition of manganese nitrate a redox reaction? Explain your answer using oxidation states. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... .............................................................................................................................. [3] [Total: 6]

6 5 The graph in Fig. 5.1 shows the relative concentrations of oxides of nitrogen and carbon monoxide discharged from the exhaust system of a car against the air : fuel ratio in a moving car. Fig. 5.1 (a) State the relationship between air : fuel ratio and relative carbon monoxide concentration emitted by the car. Explain your answer. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [3] (b) Why does the concentration of oxides of nitrogen increase when air : fuel ratio increases? ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [3]

7 (c) Catalytic converters are used in cars to remove pollutants like carbon monoxide and oxides of nitrogen. The use of catalytic converters increases the amount of carbon dioxide in the atmosphere. Describe how carbon dioxide contributes to environmental problems. Give two specific examples of the problems caused. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [4] [Total: 10] 6 Air contains a mixture of gases including the noble gases neon, argon, krypton and xenon. These noble gases are monoatomic elements. (a) State what is meant by monoatomic. ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [1] (b) State why noble gases are unreactive. ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [1] (c) State why fractional distillation can be used to separate a liquid mixture of neon, argon, krypton and xenon. ……………………………………………………………………………………………………… …….……………………………………………………………………………………………. [1] (d) State and explain which noble gas has the fastest rate of dif