VJC 2025_H1ChemistryPrelimP2_Ans

© VJC 2025 8873/02/PRELIM/25 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 ANSWERS ……………………………………………….………….. …………………………….. CHEMISTRY 8873/02 Paper 2 Structured Questions Candidates answer on the Question Paper. 29 August 2025 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Name and CT group in the spaces at the top of this page. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all the 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. For Examiner’s Use Section A 1 / 11 2 / 20 3 / 9 4 / 7 5 / 13 Section B 6 / 7 / 20 Total / 80 This document consists of 17 printed pages and 1 blank page.

2 © VJC 2025 8873/02/PRELIM/25 Section A Answer all questions from this section in the spaces provided. 1 (a) The element sodium can exist as a number of isotopes. Complete the Table 1.1 for two isotopes species of sodium. • 1 mark for correct cation • 1 mark for correct number of protons, neutrons and electrons • 2 marks. 1 mark for each correct electronic configuration (ecf) Isotopic species protons neutrons electrons electronic configuration Na𝟏𝟏 𝟐𝟑 11 12 11 1s22s22p63s1 N𝟏𝟏 𝟐𝟒 a+ 11 13 10 1s22s22p6 [4] (b) Sodium oxide, Na2O and sodium peroxide, Na2O2 are two compounds that can be produced when sodium metal is heated in oxygen under suitable conditions. Both Na2O and Na2O2 are ionic compounds. Each compound contains only one single anion and the charge on each anion is the same. (i) Write the formulae of the anions in Na2O and Na2O2. • O2– in K2O and O22– in K2O2 [1] (ii) Draw a ‘dot-and-cross’ diagram of the anion in Na2O2, showing the outer shell electrons only. • [1] (iii) Predict the relative magnitudes of the melting points of Na 2O and Na 2O2. Explain your answer. L.E.  𝑞+𝑞− 𝑟++𝑟− • Both O2– and O22– are doubly charged / same charge and O2– is smaller in size than O22-. • Hence, Na 2O has a larger magnitude of lattice energy than that of Na 2O2 [or stronger ionic bonds / electrostatic forces of attraction in Na2O]. Melting point of Na2O is higher than that of Na2O2. [2] (c) (i) When the Group 1 cation, M+, is passed through an electric field, it is deflected through an angle of +5.0. The angle of deflection is dependent on the relat