2025 YIJC H1 Chem Prelim P2 Solutions (for exchange)

©YIJC [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME TEACHER’S COPY CG H1 GROUP 1 / 2 CHEMISTRY Paper 2 Structured and Free Response Questions Candidates answer on the Question Paper. Additional Materials: Data Booklet 8873/02 XX September 2025 2 hours READ THESE INSTRUCTIONS FIRST This document consists of 16 printed pages and 1 blank page. For Examiner’s Use Section A 1 / 11 2 / 9 3 / 11 4 / 12 5 / 5 6 / 12 Section B 7 or 8 / 20 Penalty units significant figures Total / 80 Write your name and class 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. Section A Answer all questions. Section B Answer one question. 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.

©YIJC [Turn over 2 Section A Answer all the questions in this section in the spaces provided. 1 (a) Elements A, B and C are three consecutive elements from Period 3 of the Periodic Table. Element B has the successive ionisation energies as shown in Table 1.1. Table 1.1 ionisation energies / kJ mol–1 1st 2nd 3rd 4th 5th 6th 7th 8th 577 1820 2740 11600 14800 18400 23300 27400 (i) Explain how the data shows that element B belongs to Group 13. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………….[1] Largest jump in ionization energy from removing 3rd electron to removing 4th electron. 4th electron is located in an inner principal quantum shell. There are 3 valence electrons. (ii) Hence, write the full electronic configuration of B. 1s2………………………………………………………………………………………………...[1] 2s2 2p6 3s2 3p1 (iii) Explain why the first ionisation energy of element B is lower than the first ionisation energy of elements A and C. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………….[3]

©YIJC [Turn over 3 Element B (Group 13) and A (Group 2): The outermost electron in A is in the 3s subshell, while the outermost electron in B is in the 3p subshell. As the average distance from the nucleus of a 3p orbital is slightly larger than that of a 3s orbital, less energy is required to remove the 3p electron in B. Element B (Group 13) and C (Group 14): The nuclear charge of B is lower than that of C, while their shielding effect is approximately the same since both have the same number of inner electronic shells. As a result, B has a lower effective nuclear charge than C, and less energy is required to remove the outermost electron in B. (b) Oxygen and chlorine react with phosphorus to form phosphorus( V) oxide and phosphorus( V) chloride respectively. Describe the reactions when phosphorus( V) oxide and phosphorus( V) chloride are added separately to two separate beakers of water. In each case, give appropriate equations and state the likely pH of the resulting solution. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………[4] P4O10, a covalent oxide, reacts vigorously and dissolves in water to form a strongly acidic solution with a pH of 1 / 2. P4O10 + 6H2O → 4H3PO4 PCl5 undergoes complete hydrolysis to give strongly acidic solution with a pH of 1 / 2. PCl5 + 4H2O → H3PO4 + 5HCl

©YIJC [Turn over 4 (c) Group 1 elements are known as alkali metals because they are able to form alkaline solutions in water. Table 1.2 shows how some Group 1 elements react with water. Table 1.2 Group 1 element description of the reaction with water Li fizzes steadily, gradually disappears Na fizzes rapidly, melts into a ball and disappears quickly K ignites with sparks and lilac flame, disappears very quickly (i) Write an equation for the reaction between sodium and water. ..........................................................................................................................................[1] 2Na + 2H2O → 2NaOH + H2 (ii) Explain why the reaction of Group 1 metals and water becomes more vigorous down the group. …………………………………………………………………………………………………….… …………………………………………………………………………………………………….[1] Down the group, the ability to lose electrons / reducing power of the Group 1 metal increases. [Total: 11] 2 (a) In 1933, British chemists accidentally discovered that subjecting ethene to high pressure in the presence of trace amounts of oxygen resulted in the formation of a soft, white solid. This solid was identified as poly(ethene), marking the beginning of a maj or global polymer industry. Depending on the reaction condi tions, the polymerisation of ethene can produce either low-density poly(ethene) (LDPE) or high -density poly(ethene) (HDPE), each with distinct structural and physical properties. (i) Sketch the structures of LDPE and HDPE using as a simplified representation of the polymer chain. LDPE HDPE [2]

©YIJC [Turn over 5 LDPE HDPE (ii) Poly(ethene) can be used to make squeezable bottles. By considering the structure and properties of LDPE and HDPE, deduce which poly(ethene) is suitable as a material for squeezable bottles. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………….[2] LDPE. In LDPE, due to branching, chains cannot be packed closely together, resulting in less extensive instantaneous dipole induced dipole interactions between polymer chains. LDPE is therefore soft/flexible and is used to make squeezable bottles. (b) In recent years, there have been concerns worldwide about the environmental impact of catastrophic oil spills caused by oil tanker accidents at sea. Such oil spills can cause havoc to marine life and pose health hazards to the human population located in nearby coastal zones. Conventional techniques such as use of sponges are not adequate to solve the problem of massive oil spills. Sponges have high reusability but low efficiency in clearing oil from sea water as it soaks up liquid mechanically. Nanomaterials have emerged as a pot ential source of novel solution to this problem. One nanomaterial that of