2024 Prelims NYJC H2 Chem P2 (Ans)

[Turn over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS CHEMISTRY 9729/02 Paper 2 Structured 9 September 2024 2 hours Candidates answer on the Question Paper Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class in the spaces at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. 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. For Examiner’s Use 1 /12 2 /7 3 /6 4 /6 5 /11 6 /11 7 /22 Total /75 This document consists of 21 printed pages and 2 blank pages. H

2 H2 Chemistry 9729/02 NYJC J2/24 PX [Turn Over For Examiner's Use Answer all questions in the space provided. 1(a) The Periodic Table usually shows hydrogen on its own and not a member of a group. (i) Suggest why the element hydrogen could be placed at the top of Group 1. Hydrogen atom has one valence electron and it has a smaller number of protons than lithium ..................................................................................................... [1] (ii) Suggest why the element hydrogen is not placed at the top of Group 1, in terms of • its structure • one physical property related to its structure Hydrogen has a simple molecular structure with weak instantaneous dipole – induced dipole interaction between the molecules, while Group I elements have a giant metallic structure with strong metallic bonds between the metallic cations and sea of delocalised valence electrons. [1] (Difference in structure of hydrogen and Group I elements) The sea of delocalised valence electrons in Group I elements act as mobile charge carriers to conduct electricity , while hydrogen does not contain mobile charged carriers /electrons are localized in covalent bonds. Hence does not conduct electricity. [1] (Difference in Physical property for hydrogen and Group I elements, accept other physical properties like mpt/bpt etc) ..................................................................................................................... [2] The trihydrogen complex cation, H 3+, was first discovered in 1911 when J.J . Thomson was performing his cathode ray tube experiments. In 1989, H 3+ was detected in the ionosphere of Jupiter. H3+ is mainly found in interstellar space