NJC Prelims Paper 3 QP

1 NJC/H2 Chem Preliminary Examination/03/2021 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on Question Paper. Additional Materials: Data Booklet 9729/03 27 August 2021 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. Section A Answer all questions. Section B Answer one question. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 /20 2 /16 3 /24 Section B 4 /20 5 /20 Paper 3 Total /80 This document consists of 28 printed pages.

2 NJC/H2 Chem Preliminary Examination/03/2021 Section A Answer all the questions in this section. 1 (a) Nicotine (C10H14N2) is a drug present in tobacco. In aqueous solution, nicotine ionises as shown. C10H14N2 + H2O C10H15N2+ + OH− pKb (C10H14N2) = 6.0 (i) Calculate the pH of a 0.100 mol dm−3 C10H14N2 solution. [2] (ii) Suggest a suitable indicator for the titration of aqueous nicotine with HNO3(aq). Explain your answer. [2] (iii) Calculate the pH of a 5.00 dm3 solution consisting of 0.100 mol dm‒3 C10H14N2 and 0.200 mol dm‒3 C10H15N2+. [1] (iv) Calculate the number of moles of HNO3 that needs to be added to the solution in (a)(iii) to obtain a buffer solution of pH 7.40. [2] …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. ……………………………………………………………………………………………..

3 NJC/H2 Chem Preliminary Examination/03/2021 [Turn over …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. ……………………………………………………………………………………………..

4 NJC/H2 Chem Preliminary Examination/03/2021 When a cigarette is smoked, nicotine-rich blood stimulates the release of many chemical messengers including dopamine and epinephrine. OH OH OH N CH3 H OH OH NH2 epinephrinedopamine (b) (i) Name the type of isomerism exhibited by epinephrine and draw the isomers. [2] (ii) Give the structure of the product when dopamine is reacted with excess concentrated HNO3. [2] (iii) A reaction between dopamine and chloromethane, CH3Cl, forms a compound with formula C11H18NO2Cl. Suggest a structure for this compound and how the yield of this compound can be maximised. [2] (iv) Suggest a chemical test to distinguish the two chemical messengers, dopamine and epinephrine. [2] …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. ……………………………………………………………………………………………..

5 NJC/H2 Chem Preliminary Examination/03/2021 [Turn over …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. Cigarette smoke contains many harmful chemicals such as Period 4 elements, chromium, nickel and arsenic. (c) Give the full electronic configuration of chromium and arsenic. [2] ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. (d) Chromium and nickel are transition elements. (i) State what is meant by the term transition elements. [1] (ii) Suggest why the first ionisation energies of chromium and nickel are similar. [2] [Total : 20]

6 NJC/H2 Chem Preliminary Examination/03/2021 2 Baeyer-Villiger reaction is an organic reaction that forms an ester from a ketone. Pentan-2-one can be converted into propyl ethanoate using a peroxyacid, RCO3H. equation 2.1 O RCO3H O O Ester can be reduced by LiA lH4 to give alcohols. An example of the reduction of propyl ethanoate is shown below. equation 2.2 O O OHOH +LiAlH4 (a) (i) Suggest the type of reaction shown in equation 2.1. [1] (ii) Suggest the products formed when ethyl benzoate is reacted with LiAlH4. [2] …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. (b) Fig 2.1 shows a reaction scheme involving a cyclic ester, compound C. A (C6H10) step 1 B (C5H8O) RCO3H O O C LiAlH4 D Fig 2.1 (i) State the reagents and conditions required for step 1 and suggest structures for the o