2025 RI Prelims H2 Chemistry P2 QP

© Raffles Institution 2025 9729/02/S/25 [Turn Over RAFFLES INSTITUTION 2025 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9729/02 Paper 2 Structured Questions 16 September 2025 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write your name, class and index number 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 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. Do not write anything in it. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 13 2 / 15 3 / 15 4 / 16 5 / 16 Total / 75 This document consists of 24 printed pages.

© Raffles Institution 2025 9729/02/S/25 [Turn Over 2 Answer all questions in the space provided. 1 Table 1.1 lists the 7th, 8th, 9th and 10th ionisation energies, in kJ mol–1, of four consecutive elements A, B, C and D in the Periodic Table. These elements have an atomic number of less than 20. Table 1.1 element 7th ionisation energy 8th ionisation energy 9th ionisation energy 10th ionisation energy A 27 110 31 720 36 620 43 180 B 11 020 33 600 38 600 43 960 C 12 000 13 840 40 760 46 190 D 11 340 14 940 16 960 48 610 (a) Give the equation, with state symbols, for the 7th ionisation energy of B. ……………………………………………………………………………………..……………… [1] (b) Deduce which element is a noble gas. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..……………… [2] (c) (i) State the identity of A. ……………………………………………………………………………………………… [1] (ii) Complete the diagram to show the arrangement of electrons in the orbitals of an atom of A. 1s 2s 2p 3s 3p ……………………………………………………………………………………..…......... [1]

© Raffles Institution 2025 9729/02/S/25 [Turn Over 3 (d) State and explain how the 2nd ionisation energy of D compares to the 1st ionisation energy of C. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..……………… [2] Table 1.2 shows the electronegativity values of some elements. Table 1.2 element electronegativity / Pauling units phosphorus 2.2 chlorine 3.0 fluorine 4.0 (e) (i) Explain what is meant by the term electronegativity. …………………………………………………………………………………………………. ……………………………………………………………………………………………… [1] (ii) Suggest a value for the electronegativity of sulfur. ……………………………………………………………………………………………… [1]

© Raffles Institution 2025 9729/02/S/25 [Turn Over 4 A bridging hydrogen refers to a hydrogen atom which is simultaneously bonded to two other atoms in a chemical structure. In diborane, the two boron atoms form a three-centre two-electron bond with a bridging hydrogen, where two electrons are shared between three atoms. diborane  The two bridging hydrogens present in diborane are labelled as Ha.  The four other hydrogen atoms, labelled as Hb, lie on the same plane as the two boron atoms.  One of the bridging hydrogens lies above this plane while the other lies below this plane. (f) (i) State and explain how the B–Ha bond length compares to that of B–Hb. …………………………………………………………………………………………………. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ………………………………………………………………………………………………. [2] (ii) Suggest, with reasoning, a value for the Hb–B–Hb bond angle, given that experiments have confirmed that it is not 109.5. …………………………………………………………………………………………………. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ………………………………………………………………………………………………. [2] [Total: 13]

© Raffles Institution 2025 9729/02/S/25 [Turn Over 5 2 (a) Graphene comprises a single layer of carbon atoms arranged in interconnecting hexagonal planar rings while graphite is composed of multiple layers of graphene stacked on top of one another. (i) Draw a diagram to represent part of a graphene layer which contains at least 12 carbon atoms and two complete carbon rings. [1] (ii) With reference to orbital overlap and apart from the  bonds present, explain why all carbon–carbon bonds in a graphene layer are of equal length. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. ………………………………………………………………………………………………. [2]

© Raffles Institution 2025 9729/02/S/25 [Turn Over 6 Under certain conditions, graphene can be converted into two other forms, or allotropes, of carbon. These allotropes have giant molecular structure. Fig. 2.1 shows part of the structure present in one such allotrope. allotrope F Fig. 2.1 (iii) Deduce the hybridisation of carbon in allotrope F. …………………………………………………………………………………………………. …………………………………………………………………………………………………. ………………………………………………………………………………………………. [2] (iv) State and explain the difference in electrical conductivity of allotrope F and graphite. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. ………………………………………………………………………………………………. [2]

© Raffles Institution 2025 9729/02/S/25 [Turn Over 7 A representation of part of the structure of a carbon allotrope is given in Fig. 2.2. Fig. 2.2 (v) A researcher has concluded that the two structures given in Fig. 2.1 and Fig. 2.2 show the same allotrope. Explain if the researcher’s conclusion is correct. You may annotate on the given diagrams in your answer, or include any drawings, where relevant. …………………………………………………………………………………………………. ………………………………………………………………………………………………. [1] (b) One method of converting graphene to the two allotropes uses xenon difluoride. Xenon difluoride reacts with nitrogen monoxide to form nitrosyl fluoride, NOF. XeF2 + 2NO  2NOF + Xe (i) Draw a dot-and-cross diagram to show the bonding present within NOF, where nitrogen is the central atom. [1]

© Raffles Institution 2025 9729/02/S/25 [Turn Over 8 Compound H decomposes to form xenon difluoride at room temperature. In a molecule of H  there are only three elements: Xe, F and O  the ratio of F:O is 1:1  Xe has an oxidation state of +6. (ii) By considering the Valence Shell Electron Pair Repulsion theory, suggest the shape of the molecule. ……………………………………………………………………………………………… [1] (c) Bromoalkane J reacts with sodium hydroxide, under different conditions, to form three different organic products K, L and M. bromoalkane J K is the product formed