NJC Prelim P2 QP

1 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over NATIONAL JUNIOR COLLEGE SH 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer all questions on the Question Paper. Additional Materials: Data Booklet 9729/02 Tues 21 Aug 2018 2 hours READ THESE 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, graphs. Do not use staples, paper clips, glue or correction fluid/tape. 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. For Examiner’s Use 1 /8 2 /14 3 /13 4 /11 5 /14 6 /15 Penalty units Penalty sf Paper 2 /75 Answer ALL questions on the space provided. This paper consists of 18 printed pages.

2 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over

3 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over 1 The properties of elements and their compounds show similarities, differences and trends depending on the positions of the elements. (a) The elements in the third period, and their compounds, show trends in their physical and chemical properties. A sketch graph of the first ionisation energies of five successive elements in the third period is shown. (i) Sketch on the graph, the position of the ionisation energy of the two elements that come before Mg in this sequence. [1] (ii) Explain, with reference to electronic arrangements, the decreases in first ionisation energy between Mg and Al and between P and S. Mg and Al: ……………………………………………… …………………………...… …………………………………………………………………………………………… …………………………………………………………………………………………… P and S: …………………………………………………………………………….….. …………………………………………………………………………………………… …………………………………………………………………………………………… [2]

4 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over (b) The chlorides of the elements in the third period behave in different ways when added to water, depending on their structure and bonding. L is a chloride of an element in Period 3. A students investigated L and the results are as given below. • L is a white crystalline solid with a melting point of 987 K. • L dissolves in water to form a weakly acidic solution. • Addition of NaOH(aq) to an aqueous solution of L produces a white precipitate, M . (i) Identify L and M. L: ………………………………………… M: ……………………………………… [1] (ii) Write an equation to illustrate the formation of the weakly acidic solution. ………………………………………………………………………………………. [1] (c) Some reactions based on the Group 2 metal barium, Ba, are shown below. (i) State the reagent needed for each of reactions 1 and 2. Reaction 1 ……………………………………………………………………………... Reaction 2 ……………………………………………………………………………... [2] (ii) Write an equation for the formation of X. …………..………………………………………………………………………………. [1] [Total: 8]

5 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over 2 The use of Data Booklet is relevant to this question. (a) Copper(II) sulfate, an inorganic compound that has wide uses in organic syntheses and in engraving of zinc plates for inta glio printmaking, can undergo a series of reactions as shown below. (i) Identify D, E, F and G. D: ……………………………….. E : ……………………………….. F: ……………………………….. G : ……………………………….. [4] (ii) With the aid of relevant equations, account for the formation of the deep blue solution D from the pale blue precipitate. ………………………………………………………………………………………….. …………………………………………………………………………………………... …………………………………………………………………………………………... ………………………………………………………………………………………….. [2]

6 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over (b) (i) By quoting relevant data, account for the trend in the thermal stabilities from HCl to HI. ………………………………………………………………………………………….. …………………………………………………………………………………………... …………………………………………………………………………………………... [2] (ii) Identify a transition metal cation that can be used to differentiate the oxidising abilities of Br 2 and I2. Explain your answer with appropriate workings. [3] (iii) Suggest a series of steps to verify the presence of chloride and iodide ions in a mixture, given the following reagents: • Aqueous silver nitrate • Filter paper • Aqueous ammonia • Filter funnel • Aqueous nitric acid ………………………………………………………………………………………….. …………………………………………………………………………………………... …………………………………………………………………………………………... ………………………………………………………………………………………….. ………………………………………………………………………………………….. ………………………………………………………………………………………….. [3] [Total: 14]

7 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over 3 Capsaicin is an active component of chili peppers. The reaction scheme involving the formation of a derivative of Capsaicin, C17H25NO2, is shown below. A, C 6H10O4 Capsaicin derivative, C17H25NO2 Compounds A to D react with sodium metal. Compounds A and B react with aqueous sodium carbonate. Compound C, Compound D and the capsaicin derivative reacts with aqueous sodium hydroxide but does not react with aqueous sodium carbonate. Compounds B and E also react with cold acidified KMnO 4. (a) Name the functional group common to compounds A and B. ………………………………………………………………………………………………. [1] 1,4-dichlorobutane Reaction 2 Reaction 4 H2O 2-methylpropanoic acid Reaction 1 B, C 10H18O2 C, C 7H7OCl Reaction 3 D, C 7H9ON E, C 10H17OCl two-step reaction H2O

8 NJC SH2 Preliminary Examination 9729 / 02 / 18 [Turn Over (b) Compound A can be synthesised from 1,4-dichlorobutane in two steps. Suggest reagents and conditions for the synthesis, and the intermediate product for the reaction. Step 1: ……………………………………………………….. Step 2: ……………………………………………………….. Intermediate product: [3] (c) There are two functional groups in compound B. Suggest the identity of the functional group in B that reacts with cold acidified KMnO 4. Functional group that reacts with cold acidified KMnO 4 : ………………..……………… [1] (d) Hence, draw the structure of compound B in the box on pg 6 and state the