SMSS 2023 4NA Prelim P4

This document consists of 11 printed pages. ST. MARGARET’S SCHOOL (SECONDARY) Preliminary Examinations 2023 CANDIDATE NAME CLASS REGISTER NUMBER SCIENCE (PHYSICS,CHEMISTRY) SCIENCE (CHEMISTRY,BIOLOGY) Paper 4 Chemistry Secondary 4 Normal (Academic) 5105/04, 5107/04 17 August 2023 1 hour 15 minutes Additional Materials: NIL READ THESE INSTRUCTIONS FIRST Write your name, class and register number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a 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 on the question paper. Section B Answer any two questions. Write your answers in the spaces provided on the question paper. 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 11. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A 14 Section B 16 Total 30 Parent’s Signature

2 SMS(S) 2023 Section A [14 marks] Answer all questions. Write your answers in the spaces provided on the question paper. A1 A list of substances is given below. Ag Cl2 H2 MgCl2 Na2O SiO2 ZnO You may only use each substance once. From the list, choose the substance which (a) can react with both acid and alkali. (b) is produced when magnesium reacts with sulfuric acid. (c) can be dissolved in water to form a solution with pH greater than 7. (d) can displace iodine from aqueous potassium iodide. [4] [Total: 4] A2 Table 2.1 shows the number of protons and nucleons in six particles. Table 2.1 particle proton number nucleon number T 3 7 U 8 16 V 11 23 W 13 26 X 13 27 Z 18 40 (a) Which particle exists as monatomic element in nature? (b) Which particles are isotopes of the same element? (c) Which particle belongs to Group I of the Periodic Table? [3]

3 SMS(S) 2023 (d) Draw a ‘dot and cross’ diagram for the compound formed when particle W reacts with particle U, showing only the outermost electrons. [2] [Total: 5] A3 Propene can react with hydrogen, in the presence of a suitable catalyst, to form propane. The chemical equation for the reaction is as below: C3H6 + H2 → C3H8 (a) Draw the structural formula for propene in the box provided. [1] (b) Name the conditions required for the reaction between ethene and hydrogen. [1] (c) Describe a test to distinguish propene from propane. [2] propene

4 SMS(S) 2023 Propene can also react with chlorine to form dichloropropane. (d) Draw the structural formula of the dichloropropane formed. [1] [Total: 5]

5 SMS(S) 2023 Section B [16 marks] Answer any two questions from this section in the spaces provided. B4 Crystals of copper(II) sulfate, CuSO4 can be prepared using the method shown in Fig. 4.1. Fig. 4.1 shows the first three steps used to prepare the crystals. Solid Q is added in excess. Fig. 4.1 (a) What can solid Q, added to sulfuric acid to form copper(II) sulfate, be? [1] (b) Name the apparatus used to measure 50.0 cm3 of the sulfuric acid for step 1. [1] (c) What is the purpose of heating the solution gently in step 3? [1] (d) What is the purpose of adding solid Q in excess? [1] On the other hand, insoluble salts like barium sulfate, can be prepared by precipitation reaction. The equation shows the reaction between barium nitrate and potassium sulfate to form precipitate, barium sulfate. Ba(NO3)2 + K2SO4  2KNO3 + BaSO4 (e) (i) Calculate the relative formula mass of barium sulfate. Relative formula mass = [1]

6 SMS(S) 2023 (ii) At the end of the reaction, 5 g of barium sulfate is formed. Calculate the number of moles of barium sulfate formed at the end of the reaction. number of moles = mol [1] (iii) Based on the equation and your answer in (e)(ii), calculate the number of moles of barium nitrate used at the start of the reaction. number of moles of barium nitrate = mol [1] (iv) Hence, calculate the mass of barium nitrate used at the start of the reaction. mass of barium nitrate = g [1] [Total: 8]

7 SMS(S) 2023 B5 The National Environment Agency (NEA) monitors air pollution in five regions in Singapore. Air pollution levels are reported every hour on the NEA website. Table 5.1 shows the concentration of a few air pollutants at 5 pm, on 3 July 2023, for the five regions in Singapore. The Central Business District (CBD) is the financial hub, where there is a dense concentration of trading and banking offices, while the rest of the regions are mainly residential. It was raining heavily in the CBD at the time the report was generated. Table 5.1 regions sulfur dioxide (μg/ m3) nitrogen dioxide (μg/ m3) carbon monoxide (μg/ m3) North 2 27 300 South 3 9 300 East 6 27 300 West 7 28 300 Central Business District (CBD) 2 44 400 (a) In which region is the concentration of carbon monoxide the highest at 5 pm on 3 July 2023? Suggest a possible reason for the higher concentration in the region chosen. [2] (b) State a possible source of nitrogen dioxide at the CBD. [1] (c) Describe one harmful effect of sulfur dioxide on human health. [1] (d) Sulfur dioxide can dissolve in rainwater to form acid rain. (i) Describe a simple test to confirm the presence of acid in a sample of rainwater. [2]

8 SMS(S) 2023 (ii) The acid rain formed can acidify the soil and this may make it unsuitable for the growth of certain crops. Suggest a substance that can be used and explain how it can help to increase the pH of the soil. [2] [Total: 8]

9 SMS(S) 2023 B6 Different metals have different uses and can be extracted using different methods. (a) Nickel metal can be obtained via the reaction of magnesium and nickel chloride. The reaction of magnesium with nickel chloride is represented by the following equation. NiCl2(aq) + Mg(s) → MgCl2(aq) + Ni(s) (i) From the equation, which metal, magnesium or nickel is more reactive? [1] (ii) Explain your answer in (a)(i). [1] Nickel is a metal that resists corrosion and is commonly used to plate other metals to protect them. (iii) Explain how nickel can protect iron from corrosion when plated on it. [2] (b) Iron is extracted from iron(III) oxide in haematite by reduction with coke in the blast furnace shown in Fig. 6.1. Fig. 6.1 (i) Explain the importance of adding limestone into the blast furnace. [2]

10 SMS(S) 2023 Iron is an important substance used in the making of an alloy, steel. Steel is harder and stronger than iron and can be used to build bridges, construction materials and machinery. (ii) Explain why steel is harder and stronger than pure iron. [2] [Total: 8]