NYJC_H2 Chem Prelim 08 P2_Answers

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 Answers CANDIDATE NAME CLASS TUTOR’S NAME CHEMISTRY 9746/02 Paper 2 Structured 17 September 2008 1 hour 30 minutes Candidates answer on the Question Paper Additional Materials: Answer Paper 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 soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. 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 2 3 4 5 6 7 8 Total This document consists of 14 printed pages and 0 blank page. [Turn over

2 For Examiner's Use Answer all questions. 1 Aluminium chloride sublimes at 178 oC at standard pressure. The diagrams below show how the volume of aluminium chlori de varies with temperature as well as how its electrical conductivity varies with temperature at the stated constant pressures. H2 Chemistry 9746/02/NYJC J2/08 PX [Turn Over (a) Explain why aluminium chloride has zero electrical conductivity at regions D and E. For region D and E, aluminium chloride exists as simple molecules with no mobile electrons, hence do not conduct electricity. [2] 178 195 Temperature/ oC Volume of aluminium chloride Constant pressure of 2.5 atm Constant pressure of 1atm 178 195 C D Constant pressure of 2.5 atm Constant pressure of 2.5 atm Temperature/ oC Electrical conductivity 0 E 178 195 178 195 Temperature/ oC Volumeof aluminium chloride A B Constant pressure of 1 atm 195178

3 For Examiner's Use (b) Draw the displayed formula of the al uminium chloride molecule at regions A and B. Region A Region B H2 Chemistry 9746/02/NYJC J2/08 PX [Turn Over [2] (c) Suggest the physical state of t he aluminium chloride at region C . Explain your answer and hence state the significance of 195 oC. Liquid state because at 2.5 atm, the higher pressure prevents the molecules from vaporizing. Hence 195oC is the boiling point. [2] [Total: 6] 2(a) The following table shows the first ionisation energies of phosphorus, sulphur and chlorine. Element Ionisation Energy / kJ mol-1 P 1060 S 1000 Cl 1260 (i) Write an equation to represent the first ionization energy of chlorine. Cl(g) → Cl+(g) + e− .................................................