YTSS Sc(Chem) Prelim P3 QP

NAME: ( ) CLASS: YISHUN TOWN SECONDARY SCHOOL PRELIMINARY EXAMINATION 2025 SECONDARY 4 & 5 G3 SCIENCE (CHEMISTRY) (5086/3) DATE : 15 Aug 2025 DAY : Friday DURATION: 1 hr 15 min MARKS: 65 marks READ THIS INSTRUCTIONS FIRST Write your name, class and register number in the spaces provided at the top of this page. Section A Answer all the questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. You may use an approved calculator. A copy of the Periodic Table and Colours of Metal Hydroxides are printed on the last two pages. Section A Section B TOTAL This paper consists of 17 printed pages.

2 Section A Answer all the questions. 1 Choose from the following substances to answer the questions. PbSO4 Al2O3 CaSO4 Al(NO3)3 CuCO3 KOH ZnCl2 (NH4)2SO4 Each substance may be used once, more than once, or not at all. Which substance (a) gives a white precipitate that dissolves in excess aqueous ammonia. ….…………. [1] (b) reacts with both acid and alkali. ….…………. [1] (c) reacts with an acid to produce a salt, a gas and water. ….…………. [1] (d) gives out a gas that turns damp red litmus paper blue when warmed with sodium hydroxide. ….…………. [1] [4] 2 The apparatus shown in Fig. 2.1 can be used to separate hexane (boiling point 70°C) and heptane (boiling point 98°C). Fig. 2.1

3 (a) Describe the role of apparatus A. ………………………………………………………………………………………... ………………………………………………………………………………………... [1] (b) Identify the distillate first collected. ………………………………………………………………………………………... [1] (c) Describe the changes in the arrangement and movement of particles in hexane when it is heated from 25 ºC to 80 ºC. arrangement : ………………………………………………………………………………………... ………………………………………………………………………………………... movement : ………………………………………………………………………………………... .……………………………………………………………………………………….. [2] 3 The atomic radius is a measure of the size of an atom. The ionic radius is a measure of the size of an ion. The table below shows the information on the atomic and ionic radii of Period 3 elements. Silicon is excluded as it does not form ions.

4 (a) Complete the table to show the electronic structure of each ion. [2] (b) (i) State one difference between the atomic radii of metals and non- metals. ………………………………………………………………………………… ………………………………………………………………………………… [1] (ii) State one difference between the ionic radii of metal ions and non- metal ions. ………………………………………………………………………………… ………………………………………………………………………………… [1] (iii) Suggest an explanation for the difference in (b)(ii). …………………………………………………………………………………. …………………………………………………………………………………. [1] (c) Argon is also found in Period 3 of the Periodic Table. Explain why there is no value for the ionic radius of argon. …………………………………………………………………………...…………… …………………………………………………………………………………….….. [1] 4 Fig. 4.1 describes some of the substances that result from chemical reactions with solution R. Fig. 4.1 R aqueous metal salt S insoluble carbonate T green precipitate U white precipitate aqueous potassium carbonate aqueous ammonia acidified aqueous potassium manganate (VII) red-brown precipitate dilute nitric acid and aqueous barium nitrate

5 (a) Identify R, S, T and U. R ……………………………………. S …………………………………….. T ……………………………………. U …………………………………….. [4] (b) Write an ionic equation, including state symbols, for the reaction between R and aqueous potassium carbonate. ………………………………………………………………………………………... [2] (c) Describe the colour change of acidified potassium manganate (VII) when it was added to T. ………………………………………………………………………………………... ………………………………………………………………………………………... [1] 5 Molten iron may be extracted by reacting iron(III) oxide with aluminium. During the extraction, a large amount of heat is produced. This process is known as the thermite reaction. The production of molten iron in the thermite reaction is shown in the equation below: Fe2O3 (s) + 2Al (s) → Al2O3 (s) + 2Fe (l) (a) (i) Complete the table to show the oxidation states of aluminium and iron before and after the reaction takes place. element oxidation state before reaction oxidation state after reaction aluminium iron [2]

6 (ii) Using the information from the table, explain why thermite reaction is a redox reaction. …………………………………………………………………………………. ……….………………………………………………………………………… …………………………………………………………………………………. [2] (b) State, with a reason, the type of energy change that occurs during the extraction of iron in the thermite reaction. type of energy change: …..…………………………….. reason: ………………………..………………………………………………….…………… ………………………………………………………………………….…………….. [2] (c) Calculate the mass of aluminium needed to produce 1000 g of molten iron. mass : ……………………… g [2] 6 Fluorine, chlorine and bromine are found in group 17 of the Periodic Table. (a) State one physical property trend of group 17 elements. …………………………………………………………………………………...…… …………………………………………………………………………………...…… [1]

7 (b) Fig. 6.1 shows the experiment when a sample of fluorine gas is passed over potassium iodide powder under strong heat. Fig. 6.1 (i) Identify gas Z. gas Z ………………………………………................................................ [1] (ii) Explain the chemistry involved when fluorine gas is passed over potassium iodide powder under strong heat. ……………………………………………….………………………………… …………………………………………………………………….…………… ……………………………………………………………………….………… ……………………………………………………………………………….... [1] 7 (a) Sodium burns in air to form a white solid of sodium oxide. (i) Draw a ‘dot-and-cross’ diagram to show the arrangement of all electrons in sodium oxide. [2]

8 (ii) Explain, in terms of electrons, how sodium reacts with oxygen. …………………………………………………………………………………. …………………………………………………………………………………. [1] (b) Nitrogen trifluoride, NF 3, is a compound used in the manufacture of LCD displays and other microelectronics. (i) Draw a ‘dot -and-cross’ diagram to show the arrangement of valence electrons in a molecule of nitrogen trifluoride. [2] (ii) With reference to structure and bonding, explain why nitrogen trifluoride exists in the gaseous state at room temperature. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… …………………………………………………………………………………. [2] (iii) Nitrogen trifluoride is a greenhouse gas. Describe one potential impact of increased levels of greenhouse gases in our atmosphere. …………………………………………………………………………………. ………………………………………………………………………………… ………………………………...………………………………………………. [1]

9 8 Cyclohexane is a colourless liquid. The structure of cyclohexane is shown below. (a) Write a balanced chemical equation for the complete com