2024 Prelims CJC H2 Chem P2 (QP)

[Turn over 9729/02 CJC JC2 Preliminary Examination 2024 CANDIDATE NAME CLASS 2T INDEX CHEMISTRY 9729/02 Paper 2 Structured Questions 26 August 2024 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class 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. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 16 printed pages. For Examiner’s Use Paper 1 30 Paper 2 Q1 /7 Q2 /11 Q3 /13 Q4 /15 Q5 /15 Q6 /14 75 Paper 3 80 Paper 4 55 OVERALL (100%) GRADE Catholic Junior College JC2 Preliminary Examination Higher 2

2 9729/02 CJC JC2 Preliminary Examination 2024 Answer all the questions in the space provided. 1 Tetrahalosilanes have the general formula SiX4, where X represents one of the halogens. A sample of SiX4 is atomised and ionised. The ions produced are then analysed. (a) Complete the following energy level diagram to show the arrangement of electrons in the orbitals of Si+ ion. [2] (b) In the first analysis, the second ionisation energy of silicon is recorded. Write an equation for the second ionisation energy of silicon. ……..……………………………………………………………………………………….. [1] (c) Explain why the second ionisation energy of silicon is higher than that of the first. …………………..…………………………………………………………………………...… ……….…….………………………………………………………………………….......…… .…..…………………………………………………………………………………………….. .................................................................................................................................. [1] Energy 1s

3 9729/02 CJC JC2 Preliminary Examination 2024 [Turn over (d) In the second analysis, ions of X+ are analysed. A sample each of 28 + 14Si and X+ is passed through an electric field. The angles of deflection of 28 + 14Si and X+ are 5.6o and 2.0o respectively. (i) Deduce, by calculation, the identity of X. [2] (ii) Suggest why there is another beam detected with an angle of deflection of 1.9o. ……..…………………………………………………………………………………. [1] [Total: 7]

4 9729/02 CJC JC2 Preliminary Examination 2024 2 This question is about phosphorus and its compounds. (a) With reference to relevant electronic configurations where necessary, explain why the first ioni sation energy of phosphorus is higher than the elements that come immediately before and after it in Period 3. …………………..………………………..………………………………………………….... …………………..………………………………………………………………………….... …………………..…………………………………………………………………………..... …………………..………………………………………………………………………….... …………………..…………………………………………………………………………..... …………………..…………………………………………………………………………..... …………….…….…………………………………………………………………………..... …………………..…………………………………………………………………………..... …………………..…………………………………………………………………………..... …………….…….………………………………………………………………………….... ……..……………………………………………………………………………………… [3] (b) With reference to structure and bonding, explain why the melting point of phosphorus is lower than the elements that come immediately before and after it in Period 3. …………………..…………………………………………………………………………..... …………………..…………………………………………………………………………..... …………………..………………………………………………………………………….... . …………………..…………………………………………………………………………..... …………………..…………………………………………………………………………..... …………………..…………………………………………………………………………..... …………….…….…………………………………………………………………………..... …………………..…………………………………………………………………………..... …………….…….…………………………………………………………………………..... ……..……………………………………………………………………………………… [2]

5 9729/02 CJC JC2 Preliminary Examination 2024 [Turn over The most important oxide of phosphorus is phosphorus(V) oxide, P 4O10. It is a powerful dessicant and dehydrating agent. (c) Write a balanced equation for the reaction of P4O10 with water and state the pH of the resulting solution. …………….…….…………………………………………………………………………........ ……..………………………………………………………………………………………… [1] The structure of phosphorus(V) sulfide, P4S10, is closely related to that of P4O10. (d) Reaction of P4S10 with water gives two products. One of the products is the same as the product of the reaction in (c), the other product is a gaseous compound. Suggest a balanced equation for this reaction. ……..………………………………………………………………………………………… [1] (e) In vapour form, phosphorus(V) sulfide exists as P2S5 molecules. When P2S5 is heated under a vacuum together with caesium sulfide, Cs 2S, and sulfur, it produces an ionic compound R which has the following composition by mass: Cs, 58.1%; P, 6.78%; S, 35.1%. (i) Calculate the empirical formula of compound R and hence deduce its chemical formula, given that the relative formula mass, Mr, is 914.6. [2] (ii) Compound R contains Cs+ cation and an anion. Given that the cation and anion of compound R are present in a 4:1 ratio, write the formula of the anion. Anion: ………………………………………………………………………………. [1]

6 9729/02 CJC JC2 Preliminary Examination 2024 (iii) Suggest the structure of the anion, given that there are three S‒S single bonds, a plane of symmetry exists within the anion structure and the constituent atoms show their usual valencies. [1] [Total: 11]

7 9729/02 CJC JC2 Preliminary Examination 2024 [Turn over 3 Compound G is a colourless liquid with the formula CxHy(OH)z. When 3.00 x 10–4 mol of G was dissolved in an inert solvent and an excess of sodium metal added, 10.8 cm3 of hydrogen gas, H2, was produced. In a vessel with 50.0 cm3 of oxygen gas, the complete combustion of 3.00 x 10–4 mol of G is carried out. When the resultant mixture is cooled, a total volume of 46.4 cm3 of gas remains. When this gaseous mixture is passed repeatedly over NaOH(s), the final volume of gas which remains is 24.8 cm3. All volumes are measured at room temperature and pressure. (a) (i) Write the equation for the reaction of ethanol with an excess of sodium metal. ......................................................................................................................... [1] (ii) Show that the value of z for G is 3. [1] (iii) Complete the following equation for the complete combustion of G, using x and y. [1] (iv) Hence determine the value of x and y for G. [3] CxHy(OH)3(l) + (𝑥 + 𝑦+3 4 − 3 2) O2(g) → x CO2(g) + 𝑦+3 2 H2O(l)

8 9729/02 CJC JC2 Preliminary Examination 2024 (b) Compound H, is an optically inactive five-membered unsaturated cyclic compound with molecular formula C6H10O. It decolourises aqueous bromine and gives off misty acid fumes when reacted with PCl5. Upon heating H with hot concentrated KMnO4, a single product, J, C6H10O5, is formed. 1 mol of J reacts with only 3 mol of PCl5 giving misty acid fumes. 1 mol of J reacts with only 1 mol of Na2CO3 giving effervescence. (i) Name the type of reaction occurring when H reacts with aqueous bromine. …………………………………………………………………………………..……. [1] (ii) Compound J does not contain a chiral centre. Henc