YJC H1 CHEM P2

This question paper consists of 12 printed pages. YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE Parent’s Signature: CANDIDATE’S NAME: ______________________________ CTG: _____________ YISHUN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2015 CHEMISTRY 8872/02 HIGHER 1 Paper 2: Structured & Free Response Questions 18 August 2015 2 hours Additional materials: Writing papers Data Booklet INSTRUCTIONS TO CANDIDATES Write your name and CTG in the spaces at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use paper clips, highlighters, glue or correction fluid. Answer all questions. You are advised to show all working in calculations. You may use a calculator. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. For Examiner’s Use Paper 1 Total /30 Paper 2 Section A /40 B5 /20 B6 /20 B7 /20 Total /80 Overall /110

2 8872 / YJC / 2015 / Preliminary Examination / Paper 2 Section A Answer all the questions in this section in the spaces provided. 1 Nitrogen and phosphorus are elements from Group V. (a) Explain why nitrogen has a higher first ionisation energy than phosphorus. [2] (b) Ammonia, NH 3 and phosgene, PH 3 are both g aseous Group V hydrides. The boiling points of ammonia and phosgene are shown in the table below. Group V hydride Boiling point / 0C ammonia −33 phosgene −88 Explain why phosgene has a lower boiling point than ammonia. [2]

3 8872 / YJC / 2015 / Preliminary Examination / Paper 2 (c) Ammonia reacts with molecules of boron trifluoride, BF3 to form H 3NBF3. One of the bonds in H3NBF3 is a dative covalent bond. (i) Define the term dative bond. (ii) Draw a dot-and-cross diagram to show the bonding in H3NBF3. (iii) The H−N−H bond angle in ammonia is 107 0. A student predicted that the H −N−H bond angle is H3NBF3 is larger. Explain why the student might expect the H−N−H bond angle to be larger in H3NBF3 than in ammonia. [5] [Total: 9]

4 8872 / YJC / 2015 / Preliminary Examination / Paper 2 2 Compound A is found in biodiesel. It has the skeletal formula shown below. (a) Name the two functional groups that are present in compound A. [2] (b) Compound B is a geometrical isomer of compound A. Draw the structure of compound B. [1] (c) Draw the structure of the products formed when compoun d A reacts with hot aqueous sodium hydroxide. [2] O O Compound A

5 8872 / YJC / 2015 / Preliminary Examination / Paper 2 (d) A student determined the enthalpy change of combustion for compound A. In her experiment, 2.50 g of compound A was used to heat 100 g of water. The temperature rose from 25.0 0C to 56.5 0C. (i) Define the term standard enthalpy change of combustion. (ii) Given that the specific heat capacity of water is 4.18 Jg−1K−1, calculate the heat released in the experiment. (iii) The molecular formula of compound A is C17H32O2. Calculate the number of moles of compound A used in the experiment. (iv) Hence, calculate the enthalpy change of combustion of compound A. [5] [Total: 10]

6 8872 / YJC / 2015 / Preliminary Examination / Paper 2 3 In order to determine the structure o f compound C, C8H8O, chemical tests were carried out and the results are tabulated below. Test Observations 1 2,4-dinitrophenylhydrazine Orange precipitate formed 2 Tollen’s reagent Silver mirror formed 3 Fehling’s solution No precipitate formed 4 Hot acidified KMnO4 Purple KMnO4 decolourised (a) What can be deduced about the nature of compound C in the following tests? Test 1 Test 2 Test 3 [3] (b) For test 4, the structure of the organic product is Deduce the structure of compound C. [1] (c) Draw the structure of a structural isomer of compound C that will give a different observation for one of the above tests. [1] COOHHOOC

7 8872 / YJC / 2015 / Preliminary Examination / Paper 2 (d) Compound C contains a benzene ring. Describe the bonding in benzene in terms of orbitals overlap. You may draw a diagram to illustrate your answer. [3] [Total: 8]

8 8872 / YJC / 2015 / Preliminary Examination / Paper 2 4 Potassium manganate(VII), KMnO4 can be prepared in the laboratory by a two -step synthesis starting from manganese(IV) oxide, MnO2. Step 1 In this step, manganese( IV) oxide MnO 2 is heated strongly with potassium hydroxide, KOH and potassium chlorate(V), KClO3 which is a powerful oxidising agent. Manganese(IV) oxide, MnO2 is oxidised to manganate( VI) ions, MnO 4 2− while chlorate(V) ions, ClO3− are reduced to chloride ions, Cl−. Step 2 Potassium manganate(VI) is separated from the alkaline mixture from step 1 as a green solid. In this step, potassium manganate( VI) is heated in wa ter. Manganate(VI) ions disproportionate to form manganate(VII) ions and a precipitate of manganese( IV) oxide. The following equilibrium is set up. 3MnO4 2−(aq) + 2H2O(l) ⇌ 2MnO4−(aq) + MnO2(s) + 4OH−(aq) Aqueous potassium manganate(VII), KMnO4, in acidic conditions can be used in analysis. A student analyses an impure sample of sodium sulfite, Na2SO3, using the followi