2022 TSS Chem Prelims P2 SectB

No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School Name: Index Number: Class: _______ TEMASEK SECONDARY SCHOOL Preliminary Examination 2022 Secondary 4 Express CHEMISTRY 6092/02 Paper 2 (Section B) Total duration for Sections A and B: 1 hour 45 minutes Question and Answer Booklet READ THESE INSTRUCTIONS FIRST Do not open the booklet until you are told to do so. Hand in this booklet at the end of the paper. Write your name, index number and class in all the work you hand in. Write in dark blue or black pen. Answer three questions from this section. Question B9 is in the form of either/or and only one of the alternatives should be attempted. Write your answers in the spaces provided. At the end of the examination, submit Section A and B separately. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 14 of Section A. FOR EXAMINER'S USE Section B /30 This document consists of 10 printed pages.

2 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School. Section B Answer three questions from this section. Question B9 is in the form of either/or and only one of the alternatives should be attempted. Write your answers in the spaces provided. B7 Read the information about the history of the Periodic Table. Chemists spent many years trying to arrange elements in a sensible order. Johann Döbereiner was one of the first chemists to organise elements by their properties. He found out that some sets of three elements seem to fit together because they have similar properties. He called these sets of elements ‘triads’. Table 7.1 shows some elements that could be considered to be triads. Table 7.1 Triad A lithium sodium potassium Triad B calcium strontium barium Triad C chlorine bromine iodine Triad D carbon nitrogen oxygen Döbereiner looked at the relative atomic masses of the elements in some triads. He noticed that the relative atomic mass of the ‘middle’ element was close to the mean (average) relative atomic mass of the first and third element. This was a step forward but did not help with all of the other elements that Döbereiner had not put into groups of three. It was left to others to build on Döbereiner’s work. In 1864, a chemist called John Newlands had an idea of arranging the elements in order, depending on their chemical properties. He called his idea the ‘Law of Octaves’.

3 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School. Table 7.2 shows Newlands’ arrangement of some of the elements. He put elements with similar properties into the same row of his table. Table 7.2 Row Elements 1 1H 19F 35.5Cl 2 7Li 23Na 39K 3 9Gl 24Mg 40Ca 4 11Bo 27Al 52Cr 5 12C 28Si 48Ti 6 14N 31P 55Mn 7 16O 32S 56Fe Newlands based the order of the elements on their relative atomic masses. The Periodic Table that is used today was developed after Newlands’ table. The symbols that Newlands used for some of the elements are different to those on the Periodic Table today. (a) Using the triads in Table 7.1 for this question. (i) Three of the four triads now fit into Groups in the modern Periodic Table. Which triad, A, B, C or D does not? Explain your answer. ………………………………………………………………………………….. ………………………………………………………………………………….. ……………………………………………………………..……………...…[2] (ii) Use calculations to show that the elements in any one of the four triads obey the atomic mass pattern observed by Döbereiner. Show your working. ..…………………………………………………………………………...…[2]

4 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School. (b) Use the data in Table 7.2 for this question. (i) Describe the trend in relative atomic masses across Row 1 in Newlands’ table. ……………………………………………………………..……………...…[1] (ii) The numbers shown with each symbol give the atomic mass of each element. What symbols do we use today for the elements 9Gl and 11Bo in Newlands’ table? 9Gl ………………………………… 11Bo ……………………………… [2] (iii) In Newlands’ table , the elements in the rows may or may not be all together in the same groups in the modern Periodic Table. Use elements in different rows to support this statement. ………………………………………………………………………………….. ………………………………………………………………………………….. ………………………………………………………………………………….. ………………………………………………………………………………….. ……………………………………………………………………………..…[3] (iv) Newlands’ table does not include any elements from one of the groups in the modern Periodic Table. Identify the missing group and suggest why Newlands could not include these elements in his table. ………………………………………………………………………………….. ..…………………………………………………………………………...…[2]

5 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School. B8 (a) Esters are compounds which give fruits their flavours. They also provide the scent in flowers. (i) The ester CH3(CH2)2COOCH3 contributes to the aroma of apples. Draw the full structural formulae of the two starting materials needed to produce this ester. starting material 1 starting material 2 [2] (ii) Describe a chemical test to distinguish the two starting materials. ………………………………………………………………………..…………. ………………………………………..…………………………………...…..[2] (iii) One of the starting materials used for esterification must be freshly prepared and cannot be left to stand in air before the reaction. State the functional group of this starting material and explain why. ………………………………………………………………………..…………. ………………………………………..…………………………...…………..[2]

6 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School. (b) Other than esters, leaf alcohol is also commonly used in fragrances as it is responsible for the aroma of freshly cut grass. Fig. 8.1 shows the structural formula of leaf alcohol. Fig. 8.1 (i) Circle the functional group(s) of leaf alcohol in Figure 8.1 [1] (ii) When heated at 60 atm and 300°C, in presence of an acid, leaf alcohol reacts to form a product. This molecular mass of this product increased by 18. Draw the deduced structure of this product. [1] (iii) Draw two repeat units of the polymer formed by polymerisation of leaf alcohol. [2]

7 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School. Either B9 (a) Fig. 9.1 shows the reaction between di-acyl chloride and diamine to form a polymer. Fig. 9.1 Acyl chlorides reacts with amines in a similar manner as carboxylic acids. (i) Identify molecule X in Figure 9.1. ………………………………………..……………………………………..[1] (ii) State the type of polymerisation shown in Figure 9.1. Explain your answer. …………………………………………………………………………………. ………………………………………..……………………………………..[1] (iii) Name type of linkage present in the polymer formed in Figure 9.1 ………………………………………..……………………………………..[1] (iv) Explain why polymers such as that shown in Figure 9.1 are increasingly being used in place of natural materials. ………………………………………..……………………………………..[1]

8 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School. (v) Some polymers are non-biodegradable in nature.