ACSBR 4NA 5105 2024 SCCHEM prelim ANS_FINAL

Preliminary Examination 2024 Secondary Four Normal (Academic) Science (Chemistry) 5105 Paper 4 Page 1 ANSWERS TO 2024 PRELIM 5105 SCCHEM Paper 3: 1. B 16. A 2. D 17. C 3. B 18. C 4. B 19. C 5. B 20. B 6. A 7. B 8. B 9. A 10. C 11. D 12. C 13. A 14. A 15. C Paper 4: Section A Answer all the questions in this section. 1 One of the isotopes of bromine has the symbol shown. Br35 79 (a) Complete the table to show the relative mass and relative charge of the particles found in this isotope. particle relative mass relative charge electron 1/1836 OR 1/1840 1- proton 1 1+ neutron 1 0 1 mark for at least 2 correct; 2 marks for all correct; [2]

Preliminary Examination 2024 Secondary Four Normal (Academic) Science (Chemistry) 5105 Paper 4 Page 2 (b) Determine the number of each of these particles in one atom of the isotope of bromine, Br35 79 . number of electrons = ……… 35………………… number of neutrons = ……… 44………………… number of protons = ……… 35………………… [2] 1 mark for at least 2 correct; 2 marks for all correct; 2 The diagram shows how the components in petroleum (crude oil) can be separated into different fractions using fractional distillation. (a) Which of the fractions, A, B, C or D has the highest boiling point? …… D OR BITUMEN…………………………..… …… ………………………………. [1] (b) Suggest one compound likely to be present in fraction A. Methane/CH4/ethane/C2H6/propane/C3H8/butane/C4H10. ..………… [1] (c) Some fractions like diesel oil, which contain larger molecules, can be broken up into smaller molecules by a chemical reaction. C16H34 → substance E + C2H4 + C3H6 (i) Name the chemical reaction. …………… cracking…………………..……………………………….. [1] (ii) Deduce the chemical formula of substance E. ………………… C11H24……………………………………………….. [1]

Preliminary Examination 2024 Secondary Four Normal (Academic) Science (Chemistry) 5105 Paper 4 Page 3 (iii) Name and draw the structural formula of C3H6. name ……… propene………. structural formula [2] (iv) C2H4 can act as monomers to undergo polymerisation to form polyethene. Complete the structure of polyethene. [1] (d) Bioethanol is produced from sugarcanes and is considered an alternative renewable energy source to fossil fuels like petroleum. The following description for the use of bioethanol is in a student’s note