2021 C1 Promo P2 QP

This document consists of 12 printed pages. HWA CHONG INSTITUTION C1 Promotional Examination Higher 2 CANDIDATE NAME CT GROUP 21S CHEMISTRY Paper 2 Structured Questions Candidates answer on the Question Paper Additional Materials: Data Booklet 9729/02 30 September 2021 Total: 1 h 5 min INSTRUCTIONS TO CANDIDATES Write your name and CT class on all the work you hand in. Answer all questions in the spaces provided in this Question Booklet. Write in dark blue or black pen. You may use a soft pencil for diagrams and graphs only. Do not use staples, paper clips, highlighters, glue or correction fluid. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. A Data Booklet is provided. You may use a calculator. You are reminded of the need for good English and clear presentation in your answers. FOR EXAMINERS’ USE ONLY Paper 1 (24.2%) Paper 2 (38.7%) Paper 3 (37.1%) TOTAL Q1 / 8 Q1 / 20 Q2 / 12 Q2 / Q3 / 15 Q3 / 20 Deductions (s.f.) Deductions (total) Deductions (units) Deductions (margins) Deductions (others) / 20 / 40 / 35 100%

2 © Hwa Chong Institution 2021 9729/02/C1 Promo 2021 [Turn over A, 3L,1M 5(e) 1 (a) (i) The elements in Period 3 range from metals on the left of the Periodic Table to non - metals on the right. On the axes below, sketch the variations in melting point of the elements sodium to argon. melting point / oC Na Mg Al Si P4 S8 Cl2 Ar [1] DO NOT WRITE IN THIS MARGIN (ii) With reference to their structures and bonding, account for the variations in melting points of aluminium, silicon and argon. ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ………………………………………………………………………………………………[3]

3 © Hwa Chong Institution 2021 9729/02/C1 Promo 2021 [Turn over (b) A diagonal relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods (first 20 elements) of the Periodic Table, due to similar electronegativity of the elements. DO NOT WRITE IN THIS MARGIN B,H 1? (i) With reference to shielding effect and nuclear charge, explain why beryllium and aluminium are said to have similar electronegativity. ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ………………………………………………………………………………………………[2] B, M 2(b)(iii ) B,H 2(b)(iii ) (ii) AlCl3 can form a dimer, A l2Cl6, while BeCl2 can form a polymer, [BeC l2]n, where n is an integer greater than or equal to 1. Bonds are formed in a similar manner in Al2Cl6 and [BeCl2]n. Draw the L ewis structures of A l2Cl6 and [BeCl2]3 (which is a section of the polymer containing three repeating units). Al2Cl6: [BeCl2]3: [2] [Total: 8]

4 © Hwa Chong Institution 2021 9729/02/C1 Promo 2021 [Turn over 2 2-methylbut-1-ene reacts with iodobromide, IBr, at room temperature to produce two organic products which are constitutional isomers of each other. DO NOT WRITE IN THIS MARGIN A,L 11.2 (a) (a) What is meant by the term constitutional isomers? ..………………………..……………….…………………………………………………………… ..………………………..………………………………………………………………………… [1] 1A,2B, 2M, 1L 11.3(f) (b) (i) Given that X is the major product formed in the reaction above, describe the mechanism to form X. Show all charges and relevant lone pairs and show the movement of electron pairs by using curly arrows. [3] B, M 11.3(g ) (ii) Suggest the structure of the minor product formed. [1] B, M 11.3(g ) (iii) Briefly explain why X is the major product. ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ………………………………………………………………………………………………[1]

5 © Hwa Chong Institution 2021 9729/02/C1 Promo 2021 [Turn over B, M 11.2(d ) (iv) Deduce whether the sample of X formed in (b)(i) is optically active. ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ………………………………………………………………………………………………[2] DO NOT WRITE IN THIS MARGIN B, 2M, 8(b)(i) (c) (i) Samples of 2 -methylbut-1-ene were reacted with IBr. Several experiments were carried out at constant temperature and the initial rate of reaction was determined in each experiment as shown in Table 2.1 below. Table 2.1 experiment [2-methylbut-1-ene]/ mol dm–3 [IBr]/ mol dm–3 initial rate/ mol dm–3 s–1 1 0.25 0.25 1.40 × 10–4 2 0.50 0.25 2.80 × 10–4 3 1.00 0.50 1.12 × 10–3 Using the data given above, deduce the order of reaction with respect to 2-methylbut- 1-ene and to iodobromide. ………………………………………………… …….……… ……………………………… ………………………………………………………………………………………………[2]

6 © Hwa Chong Institution 2021 9729/02/C1 Promo 2021 [Turn over B, M 8(b)(iv ) (ii) State and explain whether your answer in (c)(i) is consistent with the mechanism drawn in (b)(i). ..………………………..……………….……………………………………………………… ..………………………..……………….……………………………………………………… ..………………………..……………….……………………………………………………… ..………………………..……………….……………………………………………………… ..………………………..……………………………………………………………………[1] DO NOT WRITE IN THIS MARGIN B, M 11.3(h )(i) (d) When a similar experiment was performed with Br 2 instead of IBr, the rate was found to be slower. Suggest and explain why this is so. ..………………………..……………….…………………………………………………………… ..………………………..……………….…………………………………………………………… ..………………………..……………….…………………………………………………………… ..………………………..……………….…………………………………………………………… ..………………………..…………………………………………………………………………[1] [Total: 12]

7 © Hwa Chong Institution 2021 9729/02/C1 Promo 2021 [Turn over BLANK PAGE

8 © Hwa Chong Institution 2021 9729/02/C1 Promo 2021 [Turn over 3 The solubility of a compound is the maximum mass of solute that can dissolve in 100 cm 3 of water to form a saturated solution. In a saturated solution, an equilibrium exists between the undissolved and dissolved solute. For example, KClO3(s) ⇌ KClO3(aq) Fig. 3.1 shows the relationship between the solubility of some compounds and temperature . Table 3.1 contains data on the standard enthalpy change of solution, Hosolution, of some of the compounds in Fig. 3.1. Fig. 3.1 Solubility curves of some compounds Table 3.1 compound Hosolution / kJ mol–1 KClO3 +41.4 KNO3 +34.9 K