plmgs comb chem prelim 2024 paper 4

1 [Turn over CANDIDATE NAME CLASS CLASS INDEX NO CENTRE NUMBER S INDEX NO SCIENCE 5105 & 5107/04 Paper 4 Chemistry 30 July 2024 (Taken together with Paper 3) 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number on the front cover. Write in dark blue or black ink. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighter, glue or correction fluid. Answer all questions in Section A and any one question in Section B. The use of an approved scientific calculator is expected, where appropriate. In calculations, you should show all the steps in your working, giving your answer at each stage. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is given in Paper 3. This document consists of 11 printed pages. For Examiner’s Use Only Paper Number Marks Paper 3 / 20 Paper 4 Section A / 22 Paper 4 Section B ___ / 8 Total / 50 Paya Lebar Methodist Girls’ School (Secondary) Preliminary Examination 2024 Secondary 4 Normal Academic/ G2

2 [Turn over Section A Answer all questions. 1 The arrangement of electrons in the atoms of six different elements is shown in the table below. The letters do not represent the chemical symbols of the elements. element P Q R S T U arrangement of electrons in the atoms 2.4 2.6 2.7 2.8.1 2.8.6 2.8.8 (a) Use the letters, P, Q, R, S, T and U to answer the following questions. (i) Which element has a proton number of 8? ……………………………………………………………………… [1] (ii) Which two elements are in the same group of the Periodic Table? ………………………………and………………………………… [1] (b) R and S react to form a compound with a high melting point. (i) Draw a ‘dot-and-cross’ diagram to show the arrangement of electrons in the compound formed between R and S. [2]

3 [Turn over (ii) In terms of structure and bonding, explain why the compound formed between R and S has a high melting point. ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… [2] [Total: 6] 2 Chlorine gas is bubbled into colourless sodium bromide solution as shown below. (a) The colourless sodium bromide solution turned reddish-brown. Explain why. …………………………………………………………………………… …………………………………………………………………………… [1] (b) Write the balanced chemical equation for the reaction in (a). State symbols are not required. …………………………………………………………………………… [1] [Total: 2