2024 Prelims TJC H2 Chem P2 (Ans)

9729 / TJC Prelims / 2024 DO NOT WRITE IN THIS MARGIN [Turn over TEMASEK JUNIOR COLLEGE 2024 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME H2 MARK SCHEME CENTRE NUMBER S INDEX NUMBER Chemistry 9729/02 Paper 2 Structured Questions 21 August 2024 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in bracket [ ] at the end of each question or part question. This document consists of 23 printed pages and 1 blank page. For Examiner’s Use Paper 1 /30 Paper 2 Q1 Q2 Q3 Q4 Q5 Total /75 Paper 3 /80 TOTAL (%) /100

2 DO NOT WRITE IN THIS MARGIN 9729 / TJC Prelims / 2024 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN Answer all questions in the spaces provided. 1 (a) Table 1.1 shows the successive ionisation energies of an element A. Table 1.1 ionisation energies / kJ mol−1 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th element A 945 1794 2735 4839 6056 11690 14180 17370 20550 23830 (i) Explain why the successive ionisation energies of an element always increase. [1] [1] As electrons are removed, number of electrons decrease while nuclear charge remains the same . Hence, there are stronger electrostatic forces of attraction between the nucleus and the remaining electrons and more energy is required for subsequent removal of electrons. (ii) Element A is in Period 4. Using information from Table 1.1 and the Data Booklet, identify element A. Explain your answer clearly. [2] [1] There is a significant increase in the values of the 5th and 6th ionisation energies. This means that the 6th electron is removed from an inner principal quantum / electron shell which is closer to the nucleus , and hence experiences stronger electrostatic forces of attraction. [1] This means that there are 5 valence electrons in element A, which puts it in Group 15, A is arsenic. (iii) State and explain how the first ionisation energy of element A will compare to that of the element to its right in the Periodic Table. [2] [1] Element A will have a higher first ionisation energy as the electron to be removed from element A is unpaired (4s2 4p3). [1] While the electron removed from the element to its right in the periodic table is paired (4s2 4p4). Less energy is required to remove this electron due to inter- electronic repulsion between the paired electro