Copy of SCSS Prelim 2024 Chem P2 QP

SWISS COTTAGE SECONDARY SCHOOL SECONDARY FOUR PRELIMINARY EXAMINATION O Name Academic Class 4 A Form Class Index Number Form Class 4 S CHEMISTRY Paper 2 No Additional Materials are required. 6092/02 Wednesday 28 August 2024 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your class, index number and name 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, glue or correction fluid. Section A Answer all questions. Write your answers in the spaces provided on the Question Paper. Section B Answer one question. Write your answers in the spaces provided on the Question Paper. 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 24. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A / 70 Section B / 10 Total / 80 This document consists of 23 printed pages and 1 blank page. Setter: Mr Choo Shi Qian Vetter: Mr Kat Kar Sien & Mdm Tan Pui San [Turn over Home of Thoughtful Leaders: Serve with Honour, Lead with Humility

2 Section A Answer all questions. A1 Use the list of elements to answer the questions. zinc argon fluorine copper hydrogen sodium silicon carbon Each element may be used once, more than once or not at all. (a) Name the element that forms an amphoteric oxide. …………………………………………………………………………………………………........[1] (b) Name the element that can form ions with more than one oxidation state. …………………………………………………………………………………………………........[1] (c) Name the element that can form a neutral oxide. …………………………………………………………………………………………………........[1] (d) Name the element that is unreactive. …………………………………………………………………………………………………........[1] (e) Name the element that is a good oxidising agent. …………………………………………………………………………………………………........[1] (f) Name the element that forms an oxide with a giant covalent structure. …………………………………………………………………………………………………........[1] [Total: 6]

3 A2 (a) Fig. 2.1 and Fig. 2.2 show some properties of Group 17 elements, the halogens. Fig. 2.1 shows the atomic radii and Fig. 2.2 shows the electronegativity of the Group 17 elements. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. It is usually measured on the Pauling scale, on which the most electronegative element (fluorine) is given an electronegativity of 4.0. (i) Use Fig. 2.1 to d escribe and explain the trend in atomic radii for halogens down the group. …………………………………………………………………………………………............ …………………………………………………………………………………………............ ….……………………………………………………………………………...………........[1] (ii) Use Fig. 2.1 and Fig. 2.2 to s tate and explain the relationship between atomic radii and electronegativity of the halogens. …………………………………………………………………………………………............ …………………………………………………………………………………………............ ….……………………………………………………………………………...………........[1] (iii) Predict and explain the electronegativity value of astatine, the next member of Group 17 element. …………………………………………………………………………………………............ ….……………………………………………………………………………...………........[1] Fig. 2.1 Fig. 2.2

4 (b) Table 2.1 shows the melting points and boiling points of Group 1 elements, together with the atomic radii. Table 2.1 element melting point / °C boiling point / °C atomic radii / pm Group 1 lithium 180 1330 145 sodium 98 890 180 potassium 64 774 220 rubidium 39 688 235 (i) State the trend observed in the melting and boiling points of Group 1 elements. …………………………………………………………………………………………............ ….……………………………………………………………………………...………........[1] (ii) Explain, in terms of bonding, the trend observed in (b)(i). …………………………………………………………………………………………............ …………………………………………………………………………………………............ …………………………………………………………………………………………............ …………………………………………………………………………………………............ ….……………………………………………………………………………...………........[2] [Total: 6]

5 A3 Table 3.1 shows some properties of oxyacids of chlorine. Table 3.1 name of acid chemical formula reaction with magnesium (all acids have the same concentration) oxidation state of chlorine hypochlorous acid HClO only a few bubbles seen chlorous acid HClO2 reacts readily chloric acid HClO3 vigorous perchloric acid HClO4 very vigorous (a) Suggest why these acids are known as oxyacids. ………………………………………………………………………………………..………………... ………………………………………………………………………………………..………………... …………….…….………………………………………………………………...………..……….[1] (b) Complete Table 3.1 by filling in the oxidation states of chlorine. [2] (c) State the relationship between the oxidation state of chlorine and the strength of the acids. Explain your reasoning using the information in Table 3.1. ………………………………………………………………………………………..………………... ………………………………………………………………………………………..………………... ………………………………………………………………………………………..………………... …………….…….………………………………………………………………...………..……….[2] (d) Identify the acid with the lowest electrical conductivity. Explain your answer. ………………………………………………………………………………………..………………... …………….…….………………………………………………………………...………..……….[1] [Total: 6]

6 A4 (a) Ammonia is produced by nitrogen gas and hydrogen gas during the Haber process. (i) Since nitrogen is the most abundant gas in air, explain why air is not used as a raw material during the Haber process. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………[1] (ii) Concentrated aqueous ammonia is used to make fertilisers such as ammonium sulfate, (NH 4)2SO4. Aqueous ammonia reacts with dilute sulfuric acid to form ammonium sulfate, (NH4)2SO4. 2NH3(aq) + H2SO4(aq) → (NH4)2SO4(aq) A student titrates 20.0 cm 3 of aqueous ammonia with 0.150 mol/dm 3 sulfuric acid. 10.50 cm3 of sulfuric acid is required to neutralise the aqueous ammonia. Calculate the concentration, in mol/dm3 , of the aqueous ammonia. [2]

7 (b) Table 4.1 shows some fertilisers that are necessary for healthy plant growth. Some of the elements needed by plants are nitrogen, potassium and phosphate. Table 4.1 type of fertiliser chemicals commonly used potassium-based fertilisers potassium chloride KCl nitrogen-based fertilisers ammonium nitrate NH4NO3 urea CO(NH2)2 phosphate fertilisers calcium dihydrogen phosphate Ca(H2PO4)2 calcium sulfate CaSO4 Calculate the percentage by mass of nitrogen in ammonium nitrate and urea to determine which fertiliser would give more nitrogen per kg. [2] (c) A chemical company makes salts for use in fertilisers. To make calcium sulfate, the company started with limestone, which is calcium carbonate. Briefly describe how pure calcium sulfate can be made from calcium carbonate. ………………………………………………………………………………………………..………... ………………………………………………………………………………………………..………... ………………………………………………………………………………………………..………... ………………………………………………………………………………………………..………... ………………………………………………………………………………………………..………... …………………………………………………………………...……………...……..……………[2] [Total: 7]

8 A5 A mixture of grey powder and white crystals undergoes a series of reactions as shown in Fig. 5.1. Fig