St Gabriels 2024 Prelims 4NA Sc(Chem) P4

St. Gabriel’s Secondary School 2024 ‘N’ Preliminary Examination Subject : Science (Chemistry) Paper No. : 5105/04 Level/Stream : Sec 4 Normal (Academic) Duration : 1 hour 15 minutes (Papers 3 and 4) Date : 07 August 2024 No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, register number and class clearly in the spaces above. Write in dark blue or black ink on both sides of the paper. You may use an HB 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. Section B Answer any 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. 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 11. 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. For Examiner’s Use Paper 3 20 Paper 4 Section A 22 Section B 8 Total 50 This question paper consists of 11 printed pages including this cover page. Name: ………………………………………… ( ) Class: Sec ………………..

SGSS/Sc(Chem)/P4/4NA/Prelim/2024 2 Section A (22 marks) Answer all questions. 1 J is a mixture of dyes. It has been suggested that J might be used as a food colouring . Paper chromatography was used to identify the dyes in J. The resulting chromatograms are shown below. Dyes K, L, M and N are safe for consumption. (a) Which of the dyes K, L, M and N are present in J? ………………………….... [1] (b) Which of the dyes is insoluble in water? ………………………….... [1] (c) It is suggested that mixture J can be used as a food colouring. Do you agree with the suggestion? Use the information given to explain your answer. ……………………………………………………………………………………………………… ………………………………………………………………………………………………… [1] (d) Dye M contains two components. Suggest how you can change this chromatographic technique so as to separate these components. ………………………………………………………………………………………………… [1] [Total: 4] J K L M N

SGSS/Sc(Chem)/P4/4NA/Prelim/2024 3 2 (a) (i) Complete the table for the two isotopes of chlorine. chlorine mass number number of protons in nucleus number of neutrons in nucleus 35Cl 17 37Cl 37 20 [2] (ii) Explain why 35Cl and 37Cl are isotopes. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ………………………………………………………………………………………… [1] (b) Sodium, proton number 11, and chlorine, proton number 17, react together to form sodium chloride. (i) Write the chemical formula for sodium chloride. ………………………………………………………………………………………… [1] (ii) Draw a ‘dot and cross’ diagram to show the bonding in sodium chloride. Show only the outer shell electrons. [2] (iii) Name the type of bonding in sodium chloride. ………………………………………………………………………………………… [1] [Total: 7]

SGSS/Sc(Chem)/P4/4NA/Prelim/2024 4 3 A student carried out an experiment to investigate the conditions required for iron to rust. The student weighed the nails at the start of the experiment and at the end of one week. The initial mass of the nails in each test tube was 4.0 g. The masses of the nails after one week were 4.0 g, 4.2 g, 4.4 g and 4.9 g. (a) Fill in the masses of the nails in the table correctly. test tube E F G H mass of nails after one week / g [1] (b) Explain why the mass of the nails in one of the test tubes remains unchanged after one week. ………………………………………………………………………………………………………. ………………………………………………………………………………………………… [1] (c) If the nails were not weighed after one week, what other physical evidence is there to show that the nails have rusted? ………………………………………………………………………………………………… [1] (d) Suggest one practical way to prevent iron nails from rusting. ………………………………………………………………………………………………… [1] [Total: 4]

SGSS/Sc(Chem)/P4/4NA/Prelim/2024 5 4 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. (a) Name solid Q, a substance which can be added to sulfuric acid to form copper(II) sulfate. ………………………………………………………………………………………………… [1] (b) Name a suitable apparatus that can be used to measure 50.0 cm3 of the sulfuric acid for step 1. ………………………………………………………………………………………………… [1] (c) Name the separation methods used in step 2 and step 3 step 2 ……………………………………….. step 3 ……………………………………….. [2] (d) What is the purpose of heating the solution gently in step 3? ………………………………………………………………………………………………… [1] stirring rod solid Q dilute sulfuric acid step 1 step 2 step 3 copper(II) sulfate solution copper(II) sulfate solution copper(II) sulfate crystals appear residue cool gradually Fig. 4.1

SGSS/Sc(Chem)/P4/4NA/Prelim/2024 6 (e) Insoluble salts like silver chloride, can be prepared by precipitation reaction. The equation shows the reaction between silver nitrate and sodium chloride to form precipitate, silver chloride. AgNO3 + NaCl → NaNO3 + AgCl (i) Calculate the relative formula mass of silver chloride. relative formula mass = …………………... [1] (ii) At the end of the reaction, 50 g of silver chloride is formed. Calculate the number of moles of silver chloride formed at the end of the reaction. number of moles of silver chloride = ………………….. mol [1] [Total: 7]

SGSS/Sc(Chem)/P4/4NA/Prelim/2024 7 Section B (8 marks) Answer one question from this section. 5 Six hydrocarbons are identified by the letters U, V, W, X, Y and Z. Fig. 5.1 shows how the relative molecular masses of these hydrocarbons vary with the number of carbon atoms in each of their molecules. Five of these hydrocarbons are in the same homologous series. 20 0 40 60 80 100 120 140 2 3 4 5 6 7 8 9 U V W X Y Z 160 Relative molecular mass Number of carbon atoms in each molecule of hydrocarbon Fig. 5.1 1

SGSS/Sc(Chem)/P4/4NA/Prelim/2024 8 (a) Hydrocarbon U has a relative molecular mass of 42. Suggest the name of this hydrocarbon. ………………………………………………………………………………………………. [1] (b) Which hydrocarbon, U, V, W, X, Y or Z is not a member of the same homologous series as the other five? Explain your answer. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………