CJC 2026 Prelim P3 Ans

9476/03/CJC JC2 Preliminary Examination 2026 [Turn over CANDIDATE NAME CLASS 2T INDEX NUMBER CHEMISTRY 9476/03 Paper 3 Structured Questions 14 September 2026 2 hours You must answer on the Question Paper. You will need: Data Booklet INSTRUCTIONS • Answer all questions. • Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. • Write your name, class and index number in the boxes at the top of the page. • Write your answer to each question in the space provided. • Do not use an erasable pen. Do not use correction fluid or tape. • You may use an approved calculator. INFORMATION • The total mark for this paper is 75. • The number of marks for each question paper or part question is shown in brackets [ ]. This document consists of 19 printed pages. For Examiner’s Use Section A Q1 /18 Q2 /18 Q3 /19 Section B Q4 /20 OR Q5 /20 TOTAL 75 Catholic Junior College JC2 Preliminary Examination Higher 2 WORKED SOLUTIONS

2 9476/03/CJC JC2 Preliminary Examination 2026 Section A Answer all the questions in this section. 1 (a) State how the reactivity of the halogens (from chlorine to iodine) as oxidising agents varies down the group and relate this variation to relevant Eo values from the Data Booklet. ……………………………………………………….……..………………………………………………. ……………………………………………………….……..………………………………………………. ……………………….……………………………………………………….……..……………………… …………………………………..…..……………………………………………………………………… .…………………...…….…………………..……………………………………………………...………. .………………………………………………………………………………………..……………………. ….………………………..…………………………………………………………………………………. ………..………………………………………………………………………………………..…………… …………………………………………………………………………….……..……...……………… [3] (b) Write an equation that illustrates the relative oxidising abilities of chlorine and bromine, and state the expected observations. …..…………………………………………………………………………………………...….…….…… ………..…………………………………………………………………………………………………..… ……………………………………………………………………………………………………………… ……..………………………………………………………………………………………………….…[2] (c) Ethylamine, diethylamine and triethylamine can act as Lewis bases in the gaseous phase. Describe and explain their relative basicities. ………………………………………………………………………………...……..…………………… ………………………………………………………………………………...……..…………………… ………………………………………………………………………………...……..…………………… ……………………………………………………………………...……..……………………………… …………………………………………………………...……..………………………………………… ………………………………………………...……..…………………………………………………… ……………………………………...……..……………………………………………………………… ………………...…………………………………………………………………………………………[3] Cl2 (g) + 2 e– ⇌ 2 Cl– (aq) E o = +1.36 V Br2 (l) + 2 e– ⇌ 2 Br– (aq) E o = +1.07 V I2 (s) + 2 e– ⇌ 2 I– (aq) E o = +0.54 V [1, cited E o values] The oxidising power/reactivity of the halogens decreases down the group[1], which is related to decreasing E o values from Cl2 to I2 or Cl2 is most easily reduced relating to E o value .[1]. Hence the halogen is less easily reduced down the group. 2018/P3/Q4(a) Cl2 (aq) + 2 Br– (aq) → 2 Cl– (aq) + Br2 (aq) [1] Colourless / pale-yellow solution turns orange. [1] 2018/P3/Q4(a) Or Cl2 (g) + 2 HBr (g) → 2 HCl (g) + Br2 (g) greenish-yellow gas turns reddish brown gas. Triethylamine is the most basic, followed by diethylamine and ethylamine is the weakest base. [1] Triethylamine is a tertiary (3 o) amine with three electron -donating ethyl (alkyl) groups, diethylamine has two ethyl groups and ethylamine has only one ethyl group bonded to nitrogen. [1, state that ethyl/alkyl group is electron donating] Therefore, the electron-donating effect of three ethyl groups is the greatest compared to two and one ethyl groups. The 3 electron donating ethyl groups increase the electron density on N atom, making the lone pair on of electrons on N in triethylamine most available to be donated , followed by diethylamine and then ethylamine. [1 relative number of alkyl groups and lone pair of electrons on N of triethylamine is most available for donation {LEWIS BASE}] 2022/P2/5(b)

3 9476/03/CJC JC2 Preliminary Examination 2026 [Turn over (d) Explain why amides, RCONH2, are neutral, rather than basic in aqueous solution. …………………..………………………………………………………………………………..………… ……………………………………..……………………………………………………………………..… ….………..………………………………………………………………………………………………[1] (e) Imidazole is an organic compound that is very well studied due to many natural occurring compounds, such as caffeine and histidine, containing the imidazole ring. Imidazole has six  electrons and the molecule has a planar and cyclic structure, like benzene, resulting in a ring of delocalised electrons. Two representations of imidazole are shown below. In imidazole, nitrogen atoms undergo the same hybridisation as carbon atoms. State the hybridisation of nitrogen and carbon atoms and hence suggest how the  and  bonds are formed between nitrogen and carbon atoms in an imidazole molecule with reference to orbital overlap. …..………………………………………………………………………………………………………….. …..………………………………………………………………………………………………………….. …..………………………………………………………………………………………………………….. …..………………………………………………………………………………………………………….. …..………………………………………………………………………………………………………….. …..………………………………………………………………………………………………………….. …..………………………………………………………………………………………………………….. …..……………………………………………………………………………………………………….[3] Amides are neutral as the lone pair of electrons on nitrogen atom is delocalised into the electron-withdrawing C=O group.[1], making it unavailable to accept a proton. 2018/P3/1(d) The nitrogen and carbon atoms are sp2-hybridised[1] and the head-on overlap between these hybrid orbitals, will form the five  (sigma) bonds. [1] Each of the three carbons and the two nitrogens has an unhybridised 2p orbitals , and these five 2p orbitals overlaps sideways [1] to form a delocalised p (pi) electron system like that of benzene ring. similar 2024/P3/1(d) If incorrect sp or sp3, deduct 1st mark, but award 2nd mark if any hybrid orbitals used for head-on overlap to give sigma bonds (e.c.f.).

4 9476/03/CJC JC2 Preliminary Examination 2026 (f) Imidazole is highly soluble in water. Complete the following diagram with two water molecules to show the significant force of attraction between the water molecules and imidazole. Include the name of the attraction in your diagram. [3] . (g) Kevlar is a polymer which is used in stab-proof vests and high quality bicycle tyres. A repeat unit of Kevlar is as shown. (i) Define the term polymer. …………………………………………………………………………………………….………. …………………………………………….…………………………………………………….[1] (ii) State the type of polymerisation that occurred to form Kevlar. …………………………………………………………………………………………………[1] (iii) Kevlar is synthesised in solution from the monomers A and B. Monomer A has the following structure. Draw the structure of the monomer B used to make Kevlar. [1] [1] [hydrogen bonding drawn and labelled] [1] At least between one water and imidazole [correct complete dipole and lone pair for one hydrogen bonding] [1] [correct complete dipole and lone pair for 2nd hydrogen bonding] [1] 2 out of 3 if complete dipole all shown but no lone pair. BOD for missing/incomplete dipoles on Imidazole. IF an incorrect H-bonding drawn, cannot award 3 marks. Inspired from 2021/P2/2(c)(i) Polymers are macromolecules built up from monomers, with average relative molecular mass of at least 1000 or at least 100 repeat units. [1] BOD if “average” is missing Condensation polymerisation [1]

5 9476/03/CJC JC2 Preliminar