2024 Prelims VJC H2 Chem P2 (Ans)

1 © VJC 2024 9729/02/PRELIM/24 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 ……………………………………………….………….. …………………………….. CHEMISTRY 9729/02 Paper 2 Structured Questions Candidates answer on the Question Paper. 12 September 2024 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 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. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 20 2 / 22 3 / 16 4 / 17 Total / 75 This document consists of 18 printed pages and 2 blank pages

2 © VJC 2024 9729/02/PRELIM/24 1 (a) The Pauling electronegativity values, EN, for the elements in the first two periods of the Periodic Table range from 1.0 to 4.0. The elements X, Y and Z are all in the first two periods of the Periodic Table. Their EN values are shown in Table 1.1. Table 1.1 element EN X 1.0 Y 2.1 Z 4.0 Substances exist with formulae XZ, YZ and Z2. (i) Use Table 1.1 to deduce the group of the Periodic Table that X and Z belong to. X belongs to Group 1 Z belongs to Group 17 [1] 1m: both correct (ii) Suggest the structure and bonding present in XZ. • XZ has a giant ionic structure with ionic bonds (OR electrostatic forces of attraction) between oppositely charged ions. [1] (iii) Arrange XZ, YZ and Z2 in order of increasing melting point. • Z2 < YZ < XZ [1] (b) (i) Write the full electronic configuration of an aluminium atom. • 1s22s22p63s23p1 [1] (ii) Write an equation to show the third ionisation energy of aluminium. • Al2+(g) → Al3+(g) + e– (state symbols) [1] (iii) Explain why the third ionisation energy of aluminium is greater than the first ionisation energy of sodium. • Al2+ has a greater nuclear charge than Na due to greater number of protons. The shielding effect is constant for both Al2+ and Na as they have the same electronic configuration (OR number of electrons) and involve the removal of the single electron in 3s orbital. • Hence, Al2+ has a greater effective nuclear charge and more energy is required to remove the third electron, leading to greater third ionisation energy than the first ionisation energy of sodium. [2]

3 © VJC 2024 9729/02/PRELIM/24