2026 H2 Timed Practice Paper 2 Solutions + Examiner Comments (updated 17 July)

NJC SH2 Timed Practice 9476/2/26 [Turn over NATIONAL JUNIOR COLLEGE SH2 MID YEAR TIMED PRACTICE Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer on Question Paper. Additional Materials: Data Booklet 9476/02 7 July 2026 2 hours READ THE INSTRUCTIONS FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft 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 /19 3 /15 4 /18 5 /12 6 /9 Paper 2 Total /80 This document consists of 24 printed pages.

2 NJC SH2 Timed Practice 9476/2/26 1 (a) Two organic compounds, A and B, can co -polymerise to produce a polyester. On treatment with hot acidified sodium dichromate( VI), compound A, C4H10O2, is converted into compound B. Compound B can also be formed from fumaric acid, HO2CCH=CHCO2H, upon treatment with hydrogen over a nickel catalyst (i) Draw the structures for compounds A and B. A B HOCH2CH2CH2CH2OH HO2CCH2CH2CO2H Examiner's Comment: Many students cannot recall that H2 with Ni only reduces C=C and COOH group can only be reduced by LiAlH4 in dry ether. To solve for A, students need to draw structure of B first. [2] (ii) Draw the structural formula of one repeat unit of the polymer formed from compounds A and B. [1] Examiner's Comment: Students should check if their drawn repeat unit to give the polymer when repeated. Poly(A-B) is a biodegradable plastic and can be used for food packaging like disposable tablewares and paper cups. (iii) Suggest why poly(A-B) is biodegradable. [1] Poly(A-B) has ester linkages that can be hydrolysed. Examiner's Comment: Many students did not highlight it is the presence of ester linkages which can be hydrolysed.

3 NJC SH2 Timed Practice 9476/2/26 [Turn over (b) Ethane-1,2-diol, HOCH2CH2OH, has a wide variety of uses including in antifreeze in cars. Ethane-1,2-diol undergo a series of steps to form NH2CH2CH2NH2. HOCH2CH2OH Step 1 Y ethanolic NH3 heat in sealed tube H2NCH2CH2NH2 (i) Suggest the structure of Y and state the reagents and conditions for step 1. [2] Y: BrCH2CH2Br / ClCH2CH2Cl Step 1: anhydrous PBr3 / PCl3 / PCl5 / SOCl2 or HBr (g) or HCl(g) (ii) Deduce which compound, HOCH 2CH2OH or NH 2CH2CH2NH2 has a higher boiling point. ………….…………………