2025 AMKSS EOY 3E SCI CHEM P3

1 AMKSS 3E EOY Exam 5086/03/2025 [Turn Over ANG MO KIO SECONDARY SCHOOL END-OF-YEAR EXAMINATION 2025 SECONDARY THREE EXPRESS SCIENCE 5086/03 Paper 3 Chemistry 1 October 2025 1 hour 15 minutes Setter: Mrs Joselyn Luei Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Name, Form Class and Index Number at the top of this paper. Write in dark blue or black pen. You may use an HB pencil for any diagrams of graphs. Do not use staples, paper clips, glue or correction fluid. 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 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. A copy of the Data Sheet is printed on page 18. A copy of the Periodic Table is printed on page 19. The number of marks is given in the brackets [ ] at the end of each question or part question. This document consists of 19 printed pages and 1 blank page. Candidate Name Form Class Index Number

2 AMKSS 3E EOY Exam 5086/03/2025 Section A Answer all questions. 1 Some substances are given below. hydrogen calcium oxide sulfur dioxide argon oxygen ammonia hydrogen aluminium oxide Using the substances given above, name one substance that (a) is a monatomic gas. …………………………………………………………………………………………………….. [1] (b) reacts with both acids and bases. …………………………………………………………………………………………………….. [1] (c) turns damp blue litmus paper red. …………………………………………………………………………………………………….. [1] (d) dissolves in water to form a solution with pH greater than 7. …………………………………………………………………………………………………….. [1] (e) contains an ion with the charge of +3. …………………………………………………………………………………………………….. [1] [Total: 5]

3 AMKSS 3E EOY Exam 5086/03/2025 [Turn Over 2 Using the concept of kinetic particle theory, explain the following: (a) The heating curve of ethanol is shown below. The temperature remains constant at 78°C when ethanol boils. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. [2] (b) The insecticide exists as liquid in the container and turn into gas immediately when it is released into the air by pressing the nozzle. The nozzle feels cold after this. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. [3] Temperature / °C Time / min 0 78 nozzle

4 AMKSS 3E EOY Exam 5086/03/2025 (c) The piston of the gas syringe with a blocked nozzle can be pushed in easily. If air was replaced by water, it would be harder to push the plunger. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. [3] [Total: 8] 3 Table 3.1 shows the information on 5 different atoms. The letters do not represent elements in the Periodic Table. Table 3.1 atom number of protons number of neutrons P 16 22 Q 14 14 R 16 20 S 12 14 T 18 22 (a) Which atom is stable and unreactive? Explain your answer. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. [2]

5 AMKSS 3E EOY Exam 5086/03/2025 [Turn Over (b) Which atoms are isotopes of the same element? Explain why. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. [2] (c) The ion of atom S combines with bromine to form a compound. (i) Write down the chemical formula of the ion formed by atom S. ……………………………………………………………………………………… [1] (ii) Deduce the chemical formula of the ionic compound formed when atom S combines with bromine. ……………………………………………………………………………………… [1] [Total: 6] 4 Fig 4.1 below shows students’ drawings of particles in gases. Fig 4.1 Which of the students’ drawings, A, B, C, D or E, best represents (a) molecules of steam; …………………………………………………………………………………………………….. [1]

6 AMKSS 3E EOY Exam 5086/03/2025 (b) a mixture of elements; …………………………………………………………………………………………………….. [1] (c) a mixture of compounds and an element; …………………………………………………………………………………………………….. [1] (d) a mixture of compounds. …………………………………………………………………………………………………….. [1] [Total: 4] 5 Metals such as iron and zinc can be extracted from its compounds, iron( III) oxide and zinc oxide respectively. The extraction of iron from its compound involved many stages. Stage 1: Carbon reacts with oxygen to form carbon dioxide. Stage 2: Carbon dioxide reacts with solid carbon to form carbon monoxide. (a) Write a balanced chemical equation for the reaction in stage 1 and 2. Stage 1 ….……………………………………………………………………………………….. Stage 2 ….……………………………………………………………………………………….. [2] (b) In stage 3, iron(III) oxide reacts with carbon monoxide to form iron and carbon dioxide as shown below. Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g) (i) Define the term relative molecular mass. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… [2]

7 AMKSS 3E EOY Exam 5086/03/2025 [Turn Over (ii) Calculate the relative formula mass of iron(III) oxide, Fe2O3. [1] (iii) A sample of 320 g of iron(III) oxide is reacted with excess carbon monoxide gas. Calculate the number of moles of iron(III) oxide present in the sample. [1] (iv) Calculate the volume of 6 moles of carbon dioxide gas produced in the reaction. [1] [Total: 7]

8 AMKSS 3E EOY Exam 5086/03/2025 6 (a) Choose the best method of separation to obtain the underlined substance in each of the following: crystallisation fractional distillation filtration magnetic attraction simple distillation evaporation to dryness (i) ethanol from water: ……………………………………………………………………………………………… [1] (ii) sand from sodium chloride: ……………………………………………………………………………………………… [1] (iii) pure water from salt solution: ……………………………………………………………………………………………… [1] (b) The different colours of dyes in black ink were separated. Two drops of the black ink were placed at the centre of a filter paper and allowed to dry. Drops of distilled water were slowly added to the centre of the filter paper. After some time, four coloured circles were seen, as shown in the diagram below. (i) What is the name of the separation technique used? ……………………………………………………………………………………………… [1] (ii) How many different dyes were there in the black ink? ……………………………………………………………………………………………… [1]

9 AMKSS 3E EOY Exam 5086/03/2025 [Turn Over (iii) An alternative set of apparatus for this experiment is shown below. In this case, a strip of filter paper was used and the filter paper was dipped into a water. Complete the diagram below with labels to show the results you would expect if the water is allowed to reach the lid. [2] [Total: 7] red starting line

10 AMKSS 3E EOY Exam 5086/03/2025 7 The label below has been taken from a can of Tango Sparkling Apple Drink.