NYJC H1 Chem Prelim 2012 P2

1 H1 Chemistry 8872/02 NYJC J2/12 PX [Turn Over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME CLASS TUTOR’S NAME CHEMISTRY 8872/02 Paper 2 10 September 2012 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all the questions. Section B Answer two questions on separate answer paper. 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. Section A 1 12 2 4 3 5 4 13 5 6 Total 40 This paper consists of 13 printed pages and 0 blank page

2 H1 Chemistry 8872/02 NYJC J2/12 PX For Examiner’s Use Section A Answer all the questions. Write your answers on the spaces provided. 1 Nitrides are a large class of compounds with a wide range of properties and applications. They are often used as refractory materials. Two examples are magnesium nitride, Mg3N2 and boron nitride, BN. (a) Draw a dot-and-cross diagram to show the bonding in magnesium nitride. [2] (b) Suggest the electrical conductivity of magnesium nitride in liquid state. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………….[2] (c) Boron nitride is a good lubricant like graphite. Explain, in terms of structure and bonding, this property of boron nitride. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………….[2]

3 H1 Chemistry 8872/02 NYJC J2/12 PX [Turn Over For Examiner’s Use (d) Suggest one reason why magnesium gives the nitride, Mg 3N2, in addition to its oxide when burned in air. Construct a balanced equation for the combustio n of magnesium in air. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………….[2] (e) A 2.00 g sample of the powder obtained from burning magnesium in air was boiled with water. The ammonia that was evolved neutralised 12.0 cm 3 of 0.500 mol dm−3 hydrochloric acid. (i) Construct a balanced equation for the reaction with water. …………………………………………………………………………………………….…[1] (ii) Calculate the percentage of magnesium nitride in the 2.00 g sample. [3] [Total:12]

4 H1 Chemistry 8872/02 NYJC J2/12 PX For Examiner’s Use 0 2 The formation of magnesium oxide from its elements may be represented by a Born-Haber cycle as shown below. Energy Mg2+(g) + O2−(g) / kJ mol−1 H3 +702 Mg(g) + O(g) +150 H2 −3889 Mg(s) + ½O2(g) H1 MgO(s) (a) Name the enthalpy changes represented as H1 …………………………………………………………………………………… H2 …………………………………………………………………………………[2] (b) Using values from the Data Booklet and the energy values given in the above cycle, calculate the value of H1. [2] [Total:4]

5 H1 Chemistry 8872/02 NYJC J2/12 PX [Turn Over For Examiner’s Use 3 Consider the following reversible reaction where colourless bromide ions react with hydrogen peroxide to form a reddish-brown bromine solution. 2Br− + H2O2 + 2H+ Br2 + 2H2O H < 0 (a) Explain what is meant by the term dynamic equilibrium. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………….[2] (b) Predict and explain the effect on the position of equilibrium when (i) a catalyst is added, ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… (ii) temperature is increased. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………[3] [Total:5]

6 H1 Chemistry 8872/02 NYJC J2/12 PX For Examiner’s Use 4 Cinnamaldehyde is used in fragrances for its jasmine-like odour. CH CH CHO cinnamaldehyde (a) Name the two functional groups, other than the phenyl group, that are present in cinnamaldehyde. ..................................................................................................................................[2] (b) Cinnamaldehyde can exhibit geometric isomerism. Draw and label the structure of the geometric isomers and explain how it arises. ………………………………………………………………………………………………… ……………………………………………………………………………………………….[3] (c) CH CH2CHO is a structural isomer of cinnamaldehyde. Describe a simple chemical test you could carry out to distinguish the two isomers. Draw the structure of the organic product for the positive test. [3]

7 H1 Chemistry 8872/02 NYJC J2/12 PX [Turn Over For Examiner’s Use (d) Cinnamaldehyde reacts with hydrogen gas in the presence of nickel catalyst to give a saturated compound A. (i) State the type of reaction taking place. ……………………………………………………………………………………………….[1] (ii) Draw the structural formula of compound A. [2] (e) Draw the structural formula of each of the organic products formed when cinnamaldehyde is treated with the following reagents: (i) acidified potassium dichromate(VI) when heated under reflux. (ii) 2,4-dinitrophenylhydrazine. [2] [Total: 13]

8 H1 Chemistry 8872/02 NYJC J2/12 PX For Examiner’s Use 5 Use of the Data Booklet is relevant to this question. Part of the Periodic Table is shown below. Li Be B C N O F Ne Na Mg Al Si P S Cl Ar (a) From the elements shown in the table, identify the one which exhibits each of the following property. Write your answers in the table. (i) It has the highest first ionisation energy. (ii) It has the largest ionic radius. (iii) It has an electronegativity similar to that of aluminium. (iv) It has a hydride that forms the strongest intermolecular hydrogen bonds. (v) It has a trifluoride with molecules of trigonal shape. (vi) It has a chloride that neither reacts with nor dissolves in water. (vii) It has an oxide with a giant structure and a chloride which is readily hydrolysed in water. (viii) It has an oxide that produces a strong acid when treated with water. (i) (ii) (iii) (iv) (v) (vi) (vii) (viii) [4] (b) Write equations for the reactions in (vii) and (viii). ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………….[2] [Total: 6] Group I II III IV V VI VII 0 Period 2 Period 3

9 H1 Chemistry 8872/02 NYJC J2/12 PX [Turn Over Section B Answer two questions from this section on separate answer paper. 6(a) Propan-2-ol is a clear colo urless volatile liquid. It is often used as a solvent and an antiseptic. It can be formed from the reaction between propene and steam. (i)