EJC 2026 Prelim P2 QP

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2026 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 5 – INDEX NUMBER CHEMISTRY Paper 2 Structured Questions 9476/02 27 August 2026 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Answer all questions. Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. Write and shade your index number in the spaces provided. Write your answer to each question in the space provided. Do not use an erasable pen. Do not use correction fluid or tape. The use of an approved scientific calculator is expected, where appropriate. The total mark for this paper is 75. The number of marks for each question or part question is shown in brackets [ ]. For Examiner’s Use Paper 2 1 / 13 2 / 14 3 / 11 4 / 13 5 / 24 Total / 75 This document consists of 21 printed pages and 3 blank pages.

2 © EJC 9476/02/J2PRELIM/26 1 Carbon can form both discrete molecular compounds like benzene and giant covalent networks like graphite. Neighbouring elements boron and nitrogen can combine to form isostructural analogues. One such analogue is borazine, B 3N3H6, frequently termed as inorganic benzene with the structure shown in Figure 1.1. Figure 1.1 (a) Explain why the first ionisation energy of nitrogen is higher than that of carbon, while the first ionisation energy of boron is lower than that of beryllium. ................................ ................................ ................................ ................................ ............. ................................ ................................ ................................ ................................ ............. ................................ ................................ ................................ ................................ ............. ................................ ................................ ................................ ................................ ............. ................................ ................................ ................................ ................................ ............. ................................ ................................ ................................ ................................ ............. ................................ ................................ ................................ ................................ ......... [3] (b) (i) Borazine is a volatile liquid with a density of 0.810 g cm−3. A 0.400 cm3 sample of liquid borazine is injected into a sealed 0.500 dm3 container. The container is heated to 100 ºC to ensure the sample is completely vapourised. Calculate the final pressure in the container at 100 ºC. [2]

3 © EJC 9476/02/J2PRELIM/26 [Turn Over Borazine can be synthesised via a gas -phase reaction between diborane, B 2H6, and ammonia, NH3. Their boiling points are shown in Table 1.1. Table 1.1 compound boiling point / ºC borazine, B3N3H6 55 diborane, B2H6 –93 ammonia, NH3 –33 (ii) Using the data in Table 1.1, state and explain which of the gaseous reactants, B2H6 or NH3, will show a greater deviation from ideal gas behaviour at low pressure. ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ . [2] (c) The gas phase reaction between diborane and ammonia to form liquid borazine proceeds via a series of simplified steps as shown. Step 1: B2H6(g) + 2NH3(g) → [H2B(NH3)2]+[BH4]−(s) Step 2: [H2B(NH3)2]+[BH4]−(s) → 2X(g) Step 3: 3X(g) → B3N3H6(l) + 6H2(g) (i) Write an overall chemical equation for the reaction between diborane and ammonia to form liquid borazine. ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ . [1] (ii) Given that X is a molecule, write the molecular formula of X in step 2. ................................ ................................ ................................ ................................ . [1]

4 © EJC 9476/02/J2PRELIM/26 (iii) Given that the boron atom is bonded to nitrogen atom in X, suggest the structure of X. Hence, identify the type of bond formed between the boron and nitrogen atom. Type of bond: ................................ ................................ ................................ ........... [2] (d) Borazine eliminates hydrogen gas to form a giant covalent molecule called hexagonal boron nitride (h-BN). h-BN is structurally similar to graphite. Figure 1.2 shows a layer of h-BN. Figure 1.2 Despite structural similarities, graphite is a highly efficient electrical conductor along its planar sheets while hexagonal boron nitride is an excellent electrical insulator. (i) Using Figure 1.2, state how many electrons occupy the  system in a single B3N3 ring. ................................ ................................ ................................ ................................ . [1] (ii) Using the difference in electronegativit y between boron and nitrogen , s uggest why graphite is a good electrical conductor while hexagonal boron nitride is an electrical insulator. ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ . [1] [Total: 13]

5 © EJC 9476/02/J2PRELIM/26 [Turn Over 2 Scientists are studying the use of an electrochemical cell composed of a Zn2+/Zn half-cell and a I2/I– half-cell as a possible safer option to the lithium-ion battery, which can pose a fire hazard if stored incorrectly. To test if the cell works, its voltage and the discharge rate were investigated. (a) (i) Define standard cell potential, cellE  . ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ ..... ................................ ................................ ................................ ................................ . [1] (ii) Draw a fully labelled diagram of the experimental set-up that could be used to measure the cellE  for a cell made from a standard Zn2+/Zn half-cell and a standard I2/I– half-cell. Include the direction of electron flow. [3] (iii) Use the Data Booklet to calculate the cellE  of the reaction for the electrochemical cell in (a)(ii). [1]

6 © EJC 9476/02/J2PRELIM/26 (b) During the discharging process, the cell pote