2024 Prelims YIJC H2 Chem P3 (QP)

©YIJC [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CG INDEX NO CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 12 September 2024 2 hours READ THESE INSTRUCTIONS FIRST This document consists of 32 printed pages. For Examiner’s Use Section A 1 / 21 2 / 18 3 / 21 Section B 4 or 5 / 20 Penalty units significant figures Overall / 80 Write your name, class and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. 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. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all the questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

2 ©YIJC [Turn over Section A Answer all the questions in this section. 1 (a) The tripeptide A is made by reacting amino acids B, C and D together. Table 1.1 shows the pKa values of the different functional groups present on each amino acid. Table 1.1 amino acid pKa of –carbonyl group pKa of –amino group pKa of side chain B 2.09 9.10 − C 1.88 9.60 3.65 D 2.02 8.80 − (i) Explain the term -amino acid. [1] (ii) One of the amino acids, B, present in the tripeptide A contains more than one chiral carbon atom. Draw the displayed formula of B. [1] (iii) Draw the predominant species of C at pH 4.0. [1] (iv) Suggest a pH at which the predominant species of C is a zwitterion using the information in Table 1.1. [1] (v) Explain why the side-chain of D does not have a Ka value. [1]

3 ©YIJC [Turn over

4 ©YIJC [Turn over (b) 1,2-diaminopropane can be synthesised from