2025 CCHY Prelim P2 QP

This document consists of 22 printed pages, INCLUDING the cover page and 1 blank page. [Turn over Ex 2025 Preliminary Examination Secondary Four Express CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 6092/02 Paper 2 19 August 2025 Candidates answer on the Question Paper. Additional Materials: NIL 1 hour 45 minutes 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 are to use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, glue, correction fluid or correction tape. 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 22. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A Section B Total O CHUNG CHENG HIGH SCHOOL (YISHUN)

2 CCHY 2025 6092/02/Sec4Express/Prelim/2025 BLANK PAGE

3 CCHY 2025 6092/02/Sec4Express/Prelim/2025 Section A Answer all questions. 1 Fig. 1.1 shows part of the Periodic Table. Fig. 1.1 Select elements from Fig. 1.1 to answer the following questions. You may use each element once, more than once or not at all. Write down the symbol for an element which (a) forms a stable ion by losing three electrons, ………………………………………………………………………………….……….[1] (b) exists as diatomic molecules, ………………………………………………………………………………….……….[1] (c) forms an ion which gives a red-brown precipitate on additon of aqueous ammonia, ………………………………………………………………………………….……….[1] (d) has chemical properties similar to those of magnesium, ………………………………………………………………………………….……….[1] (e) has a giant covalent structure, ………………………………………………………………………………….……….[1] (f) reacts with sodium to form an ionic compound with Mr less than 70. ………………………………………………………………………………….……….[1] [Total: 6]

4 CCHY 2025 6092/02/Sec4Express/Prelim/2025 2 Fig. 2.1 shows the label on a bottled mineral water. ions present mol/dm3 Ca2+ 20 K+ 30 Na+ 145 H+ 185 OH- 225 HCO3- 289 SO42- 410 dry residue at 180oC 210 mol/dm3 Fig. 2.1 (a) Suggest whether the bottled mineral water is acidic, alkaline or neutral. Explain your reasoning. …………………………………………………………………………………………….. …………………………………………………………………………………………..[2] (b) State the name and formulae of two salts that could be present in the bottled mineral water. name of salt formula of salt salt 1 salt 2 [2] (c) Describe how the dry residue is obtained from the bottled mineral water. ………...……………………………………………………………………………...…[1] [Total: 5]

5 CCHY 2025 6092/02/Sec4Express/Prelim/2025 3 Fig. 3.1 shows a strip of moist Universal Indicator paper pasted in a hollow cylindrical tube. Fig. 3.1 One cotton ball is soaked with concentrated hydrochloric acid which will produce hydrogen chloride gas. The other cotton ball is soaked with concentrated aqueous ammonia which will produce ammonia gas. Both cotton balls are inserted at both ends of the cylindrical tube simultaneously. When no more changes are observed on the Universal Indicator paper, the cotton balls are removed, and the Universal Indicator paper is taken out. The results are shown in Fig. 3.2. Fig. 3.2 Region P is uniformly of one colour and region R of another colour. (a) Suggest identity of X and Y. Explain your answer. …………………………………………………………………………………………….. …………………………………………………………………………………………….. ………………………………………………………………………………………......… ………...……………………………………………………………………………...…[3] (b) State the colours of region P and region R. Region P: …………………………. Region R: ………………………….. [2] (c) Region Q remains green throughout the experiment. Explain why. ………………………………………………………………………………………......… ………...……………………………………………………………………………...…[1] [Total: 6]

6 CCHY 2025 6092/02/Sec4Express/Prelim/2025 4 Table 4.1 shows information about the atomic radii and ionic radii of some Group 1 and Group 17 elements. Table 4.1 element atomic radius/pm ionic radius/pm lithium 152 68 sodium 185 98 chlorine 99 181 bromine 115 196 (a) Describe, in terms of electron loss and gain, how and why a lithium atom reacts with a chlorine atom. …………………………………………………………………………………………….... …………………………………………………………………………………………….... …………………………………………………………………………………………….... ……………………………………………………………………………………………[2] (b) Describe and explain, in terms of electron shells, the change in radius when a lithium atom forms a lithium ion. …………………………………………………………………………………………….... …………………………………………………………………………………………….... …………………………………………………………………………………………….... ……………………………………………………………………………………………[2] (c) What would you observe when aqueous bromine is added to lithium chloride solution? Explain your answer. …………………………………………………………………………………………….... …………………………………………………………………………………………….... …………………………………………………………………………………………….... ……………………………………………………………………………………………[2] [Total: 6]

7 CCHY 2025 6092/02/Sec4Express/Prelim/2025 5 Climate change is become increasingly severe, leading to more frequent weather events. To reduce the amount of pollutants in the air, countries around the world has made it compulsory for catalytic converters to be installed in vehicles and encouraged the planting of more trees. (a) Within a catalytic converter, the following reactions take place. 2CO + 2NO → 2CO2 + N2 2C8H18 + 25O2 → 16CO2 + 18H2O (i) Explain how catalytic converter reduces the amount of pollutants released in the air. ……………………………………………………………………………………... …………………………………………………………………………………..[1] (ii) Explain why the catalytic converter does not solve all the environmental problems caused by the pollutant gases in the exhaust emissions from cars. ……………………………………………………………………………………... …………………………………………………………………………………..[1] (b) Suggest two reasons why planting more trees does not solve the problem of global warming caused by the use of vehicles. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………[2]

8 CCHY 2025 6092/02/Sec4Express/Prelim/2025 (c) Ethanol can also be used as a car fuel. In some countries, it is produced from the sugars in the sugar cane. An environmentalist claims that ethanol as a fuel is ‘carbon neutral’ because using it does not add to the amount of carbon dioxide in the atmosphere. Explain why this is true. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………[3] [Total: 7]

9 CCHY 2025 6092/02/Sec4Express/Prelim/2025 6 Three experiments are conducted using iron, manganese and chromium and the observations from each experiment are recorded. Experiment 1: The metals are added separately into flasks of dilute sulfuric acid. Experiment 2: The metals are heated strongly in air. Experiment 3: Strips of the metals are added into flasks of metal salt solutions. The results for Experiments 1 and 2 are shown in Table 6.1. Table 6.1 metal experiment 1 experiment 2 iron metal dissolves slowly with effervescence, a pale green iron(II) sulfate solution is formed burns in air to form a dark brown iron(III) oxide solid manganese metal dissolves very quickly with effervescenc