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 P