2023 VJC H2 Chem Prelim P2 (QP)

© VJC 2023 9729/02/PRELIM [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATIONS Higher 2 ……………………………………………….………….. …………………………….. CHEMISTRY 9729/02 Paper 2 Structured Questions Candidates answer on the Question Paper. 15 September 2023 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your index number, 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. 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 / 7 2 / 18 3 / 10 4 / 15 5 / 15 6 / 10 Total / 75 This document consists of 24 printed pages and 2 blank pages.

2 © VJC 2023 9729/02/PRELIM 1 (a) State three ways in which an ideal gas differs from a real gas. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. ……………………...………………………………………………………………….............. [3] (b) (i) Draw a labelled diagram to show the significant force of attraction between two molecules of hydrogen fluoride. Include the name of the attraction in your diagram. [2]

3 © VJC 2023 9729/02/PRELIM [Turn over (ii) The value of pV/RT is plotted against p for 1 mol of an ideal gas and 1 mol of fluorine gas at 300 K, where p is the pressure and V is the volume of the gas. On the same axes, sketch the variation of pV/RT against p for one mole of hydrogen fluoride, HF, at the same temperature of 300 K. Briefly explain your answer. ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... [2] [Total: 7] pV/RT p 1.0 ideal gas fluorine

4 © VJC 2023 9729/02/PRELIM 2 (a) The type of bonding present in a binary compound can be predicted from the electronegativities of the elements involved. This can be shown on a van Arkel - Ketelaar triangle in Figure 2.1, which plots the difference in electronegativity, ∆𝜒, on the y-axis against the average electronegativity of the two elements, 𝜒̅, on the x-axis. In this triangle, the three corners represent the extremes of metallic, ionic, and covalent bonding, with caesium (Cs), caesium fluoride (CsF) and fluorine (F2) at these corners. Figure 2.1 (i) Describe and explain the variation in electronegativity across the third period of the Periodic Table. ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... [2] ionic metallic covalent × Cs F2 Difference in electronegativity ∆𝜒 Average electronegativity 𝜒̅ CsF × ×

5 © VJC 2023 9729/02/PRELIM [Turn over (ii) State the type of bonding present in sodium fluoride (NaF), silicon tetrafluoride (SiF4) and the magnesium-aluminium alloy (Mg-Al). Type of bonding in NaF: ………………………………… Type of bonding in SiF4: ………………………………… Type of bonding in Mg-Al: ………………………………. [2] (iii) Mark the approximate positions of NaF and SiF4 on Figure 2.1 [2] (b) Lattice energies can be obtained from constructing a Born-Haber cycle with the aid of experimental data. They can also be calculated theoretically from knowledge of the distances between the cations and anions in the crystal structure and the charge on each ion. Table 2.1 shows the values of lattice energies for some compounds. These have been either determined from experimental data or theoretically calculated. Table 2.1 compound experimental value / kJ mol─1 theoretical value / kJ mol─1 NaCl −781 −766 NaBr −743 −730 NaI −699 −685 CaCl (non-existent compound) − −687 CaCl2 − − AgF −967 −824 AgI −889 −618 (i) Define, with the aid of an equation, the lattice energy of CaCl2. ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... [2]

6 © VJC 2023 9729/02/PRELIM (ii) The given data show the l attice energies of the sodium halides becoming less exothermic from NaCl to NaI. By quoting relevant data from the Data Booklet, predict and explain whether you expect the lattice energy of CaC l2 to be more or less exothermic than that of NaCl. ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... [2] (iii) A larger difference between the experimental and theoretical values of the lattice energy is observed for AgI as compared to that for AgF. Suggest why. ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... [2]

7 © VJC 2023 9729/02/PRELIM [Turn over (iv) Using the data below as well as relevant data from Table 2.1 and the Data Booklet, construct a Born -Haber cycle in the grid provided and calculate the enthalpy change of formation of solid calcium(I) chloride, CaCl(s). enthalpy change of atomisation of calcium = +178 kJ mol−1 first electron affinity of chlorine = −349 kJ mol−1 Energy / kJ mol–1 [3]

8 © VJC 2023 9729/02/PRELIM (v) Calcium(I) chloride is not known to exist as it readily reacts as shown in the following equation. 2CaCl(s) → Ca(s) + CaCl2(s) State, with justification, the type of reaction that has occurred. ……………………...…………………………………………………………………... ……………………...…………………………………………………………………... ………………