2023 TJC H2 Chem Prelim P2 (QP)

9729 / TJC PRELIM / 2023 DO NOT WRITE IN THIS MARGIN [Turn over TEMASEK JUNIOR COLLEGE 2023 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CIVICS CLASS /22 CENTRE NUMBER S INDEX NUMBER Chemistry 9729/02 Paper 2 Structured Questions 23 August 2023 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Centre number, index number, name and CG 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 17 printed pages and 3 blank page. For Examiner’s Use Paper 1 /30 Paper 2 Q1 Q2 Q3 Q4 Q5 Q6 Total /75 Paper 3 /80 TOTAL (%) /100

2 DO NOT WRITE IN THIS MARGIN 9729 / TJC PRELIM / 2023 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 Atoms and ions of elements are made up of the three subatomic particles, protons, electrons, and neutrons, in varying amounts. (a) Complete the following table to show the number of each particle in 7Li+ and 14C2–. [2] Ion protons electrons neutrons 14C2– 7Li+ (b) Separate beams of 14C2– and 7Li+ ions are passed through an electric field in the set-up below. The angle of deflection of the 14C2– beam is 7.0o. Sketch on the diagram below, the paths taken by beams of 7Li+ and 14C2– ions in the presence of an electric field. Label your sketch clearly. [2] [Total: 4]

3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9729 / TJC PRELIM / 2023 DO NOT WRITE IN THIS MARGIN [Turn over 2 (a) (i) Explain what is meant by the term ‘electronegativity’, and how it relates to the concept of bond polarity. [2] (ii) State and explain the change in electronegativity across a period in the Periodic Table. [2] (iii) Explain, in terms of electronegativity why the bonding in NaC l is different from the bonding in PCl5. [1]

4 DO NOT WRITE IN THIS MARGIN 9729 / TJC PRELIM / 2023 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (b) Period 3 elements react with chlorine gas, Cl2 (g), to form chlorides. The chlorides of the elements in the third period behave in different ways when added to water, depending on their structure and bonding. The table shows the differences in observations which occur when three Period 3 chlorides are added to water. Period 3 chloride Observations when added to excess water pH of solution formed with water NaCl White solid disappears. Colourless solution obtained. 7 PCl5 Colourless solution obtained. 1 Liquid Q Vigorous reaction with cold water. White solid and pale yellow solution obtained. 1 (i) Explain in terms of bonding, why NaC l and PC l5 behave differently when added to water. Write equation for any reaction that occurs. [2] (ii) PCl5 also reacts with limited amount of water. Write the equation for the reaction. [1] (iii) State the identity of Q. [1]

5 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9729 / TJC PRELIM / 2023 DO NOT WRITE IN THIS MARGIN [Turn over (c) Phosphorus(V) chloride, PCl5, is involved in the following reaction scheme. Suggest the reagents and conditions for steps I, II and IV and the products W to Z below. [7] Z W X Y Step I : Step II : Step IV : [Total: 16] IV I II III PCl5 V

6 DO NOT WRITE IN THIS MARGIN 9729 / TJC PRELIM / 2023 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 3 Group 2 elements of the Periodic Table are also known as the alkaline earth metals. The metals are named after their oxides, the alkaline earths. "Earth" was a term applied by early chemists to non-metallic substances that are insoluble in water and resistant to heating. Fig. 3.1 shows some reactions of the Group 2 element magnesium and its compounds. Fig. 3.1 (a) MgCO3(s) undergoes thermal decomposition in Reaction 1. Describe and explain the trend in thermal stability of Group 2 carbonates in terms of the charge density of the cation and polarizability of the large anion. [2] (b) Write an equation for Reaction 3. Explain the relative reactivity of the Group 2 elements (magnesium, calcium and barium) with water, and relate this reactivity to relevant Eo values. [3]

7 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9729 / TJC PRELIM / 2023 DO NOT WRITE IN THIS MARGIN [Turn over (c) In Reaction 2, Mg(OH) 2(s) is precipitated when Ca(OH) 2(aq) is added to MgC l2(aq). No precipitate is observed when Ca(OH)2(aq) is added to BaCl2(aq) Explain the difference in observations in terms of lattice energy. [2] (d) Describe and deduce from Eo values, the relative reactivity of Group 17 elements (chlorine to iodine) as oxidising agents. Hence, state the colour of the resultant solution when 1 cm3 of MgCl2(aq) is added to 1 cm3 of Br2(aq) in a test-tube. [3]

8 DO NOT WRITE IN THIS MARGIN 9729 / TJC PRELIM / 2023 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (e) Element X is a Period 5 element. X reacts with oxygen to form an insoluble white oxide that has a melting point of 1900 C. The oxide of X conducts electricity only when in liquid state. The chloride of X acts as a Lewis acid. It forms an acidic solution when dissolved in water. (i) Suggest the structure of the oxide of X. Explain your answer. [2] (ii) Suggest the structure shown by the chloride of X and identify X. [2] [Total: 14]

9 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THI