2022 TJC Prelims H2 Paper 2 Structured Qns and Ans

9729 / TJC Prelims / 2022 DO NOT WRITE IN THIS MARGIN [Turn over TEMASEK JUNIOR COLLEGE 2022 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME WORKED SOLUTIONS CENTRE NUMBER S INDEX NUMBER Chemistry 9729/02 Paper 2 Structured Questions 25 August 2022 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name in the spaces at the top of this page. 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 the 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 brackets [ ] 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 /9 Q2 /14 Q3 /10 Q4 /8 Q5 /20 Q6 /14 Total /75 Paper 3 /80 TOTAL (%) /100

2 DO NOT WRITE IN THIS MARGIN 9729 / TJC Prelims / 2022 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN Answer all the questions in the space provided. 1 (a) Element W is from Period 5 of the Periodic Table. The first eight ionisation energies of element W, in kJ mol-1, are 869 1800 2690 3610 5720 6670 12000 13800 (i) Identify element W and explain your answer. [2] ✓ Element W is Tellurium/ Te. Electronic configuration: [Kr]4d105s25p4. ✓ There is a large difference between the 6th and 7th ionisation energies of W. ✓ The 7th electron is from an inner electronic shell. ✓ W has 6 valence electrons, hence it is from Group 16. 2 ticks – 1 mark (ii) Explain the difference between the first ionisation energy of element W compared to the element to its left on the Periodic Table. [2] ✓ 1st ionisation energy of Te involves the removal of paired 5p electrons ✓ which experiences inter-electronic repulsion. ✓ Less energy is needed to remove the electron from W/ Te than the valence electron/ unpaired 5p electron in Sb/ element to its left. ✓ IE of element W is lower. 2 ticks – 1 mark (b) The chlorides of elements in Period 3 of the Periodic Table show different behaviours on addition to water. (i) Describe and explain the reactions of aluminium chloride, A lCl3, and phosphorus pentachloride, PCl5, with excess water. Write equations for any reactions that occur. [3] AlCl3 undergoes hydration and hydrolysis. ✓ Hydrolysis take place as Al3+ has a high charge density hence a high polarising power. ✓ Al3+ draws electrons from its surrounding water molecules and weakens the O-H bond. It is easier for a H+ ion to leave the water molecule. ✓ AlCl3 + 6H2O