SSS Chem 5105, 5107 Prelim 2021 P4 Final

5105/5107/04/Prelim/21 [Turn over SINGAPORE SPORTS SCHOOL PRELIMINARY EXAMINATION SECONDARY 4 NORMAL (ACADEMIC) ___________________________________________________________________ SCIENCE 5105/04; 5107/04 Paper 4 (Chemistry) 16 AUGUST 2021 Papers 3 and 4: 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. _________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your class, index number and name on all the work you hand in. Write in a dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in Section A and any two questions in Section B. The use of an approved scientific calculator is expected, where appropriate. In calculations, you should show all the steps in your working, giving your answer at each stage. You are advised to spend no longer than 30 minutes on Paper 3. You may proceed to answer Paper 4 as soon as you have completed Paper 3. A copy of the Periodic Table is printed on page 10. At the end of the examination hand in your answers to Paper 3 and Paper 4 separately. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 9 printed pages and 1 blank page. CANDIDATE NAME CLASS INDEX NUMBER For Examiner’s Use Section A / 14 Section B /16 Total 30

2 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use Section A Answer all the questions in the spaces provided. 1 Sulfur is an element in Group VI of the Periodic Table. (a) Define the term element. [1] (b) The diagram below shows how the temperature changes as a sample of solid sulfur is heated. (i) What is the boiling point of sulfur? boiling point: °C [1] (ii) Between which two letters is there only solid present? and [1] (iii) In terms of kinetic particle theory, explain what happens in the region from B to C. [2] [Total: 5]

3 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use 2 The electronic structures of five atoms are given below. Answer the following questions about these atoms. Each atom may be used once, more than once or not at all. Which atom A, B, C, D or E, (a) has a total of 8 electrons, [1] (b) is in Group III of the Periodic Table, [1] (c) has 11 protons in its nucleus, [1] (d) is a noble gas, [1] (e) forms a stable ion with a 1– charge? [1] [Total: 5] 3 The diagram shows part of the structures of two substances X and Y, at room temperature and pressure. (a) In the space below, draw the “dot-and-cross” diagram for a molecule of substance Y. Show only the valence electrons. [2]

4 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use (b) Explain why substance X has a higher melting point than substance Y. [2] [Total: 4]

5 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use Section B Answer any two questions from this section in the spaces provided. 4 (a) Iron is extracted in the blast furnace commercially. (i) What three raw materials are added to the top of the furnace? 1. 2. 3. [2] (ii) The waste gases from the blast furnace are tested using the following. The results are shown in the table below. test conducted observation limewater white precipitate lighted splint flame put out, no ‘pop’ sound heard blue litmus paper turned red glowing splint did not relight What are two conclusions that can be made from these results? 1. 2. [2] (b) A student investigated the reactivity of four metals G, H, K, L, by reacting them with steam and cold water. The results are shown in the table. Metal Reaction with water Reaction with steam G  (slowly)  H   K   L  (very quickly) 

6 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use (i) Arrange the four metals in order of decreasing reactivity. [2] (ii) Name a metal that could be metal K. [1] (ii) A gas is produced when metal L reacts with water. Name this gas. [1] [Total: 8] 5 A student prepared magnesium sulfate (MgSO4) crystals starting from magnesium carbonate. The student carried out the experiment in the following steps. Step 1: Excess magnesium carbonate was added to a small volume of dilute sulfuric acid until no more magnesium carbonate would react. Step 2: The resulting mixture was filtered and the filtrate was collected. Step 3: The filtrate was heated until it was saturated. Step 4: The hot filtrate was left to cool to room temperature and the crystals formed were removed. (a) How did the student know that no more magnesium carbonate would react? [1] (b) Identify the residue in step 2. [1] (c) Name the method used to obtain the crystals formed in step 4. [1]

7 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use (d) What should the student do to ensure the crystals collected in step 4 were without contaminants? [1] (e) Write a balanced chemical equation for this reaction. Include state symbols. [2] (f) 2.4g of magnesium sulfate crystals were collected at the end of the experiment. Calculate the number of moles of magnesium sulfate in 2.4g of magnesium sulfate. [2] [Total: 8] 6 Linoleic acid is an essential polyunsaturated fatty acid found mainly in plant oils like sunflower oil. It has the following structural formula. (a) What is meant by the term polyunsaturated? [2] (b) Describe a chemical test that proves that linoleic acid is unsaturated. Chemical test: Result: [2]

8 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use (c) The relative molecular masses and the number of carbon atoms of group of hydrocarbons are given below. Number of carbon atoms per molecule of hydrocarbon 1 2 3 4 5 6 7 Relative molecular mass 16 26 44 58 ? 86 100 (i) Plot a graph pf relative molecular mass against the number of carbon atoms per molecule of hydrocarbon, marking each point with a cross (x). [1] (ii) Draw a line of best fit taking into account all your plotted points. [1] (iii) Use your graph to find the relative molecular mass of the hydrocarbon with 5 carbons. Relative molecular mass = …………… [1] (iv) One relative molecular mass value is not correct. Circle it in your graph. [1] [Total: 8] ------- End of Paper ------

9 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use [This page is intentionally left blank.]

10 5105/5107/04/Prelim/21 [Turn over For Examiner’s Use