NYJC H2 Chem Prelim 08 P2

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 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. .............................................................................................................................. ...... .............................................................................................................................. ...... .............................................................................................................................. ...... .............................................................................................................................. ..[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 [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. .............................................................................................................................. ...... .............................................................................................................................. ...... .............................................................................................................................. ...... .............................................................................................................................. ..[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. ................................................................................................................... [1] (ii) Why is the ionisation energy of sulphur lower than that of phosphorus? ....................................................................................................................... ....................................................................................................................... ....................................................................................................................... ................................................................................................................... [2] H2 Chemistry 9746/02/NYJC J2/08 PX [Turn Over

4 For Examiner's Use (b) The graphs below show the pH of the so lutions obtained after reaction (if any) of chlorides and oxides of some Period 3 elements with water. pH of solution 7 0 Na Mg Al Si P S oxides chlorides (i) Explain why aqueous sodium chloride ha s a pH of 7. Include any relevant equations in your answer. ....................................................................................................................... ....................................................................................................................... ....................................................................................................................... ................................................................................................................... [2] (ii) Use the graph above and data from the Data Booklet to predict the pH of aqueous BeCl 2. Explain your reasoning ....................................................................................................................... ....................................................................................................................... ....................................................................................................................... ................................................................................................................... [2] (iii) Give the formula of an oxide of sul phur and give the oxidation state of sulphur in this oxide. Give a balanced equation to account for the pH of its aqueous solution. Formula of oxide:............................................................................................ Oxidation state of sulphur in oxide:................................................................. Equation: .................................................................................................... [3] [Total: 10] H2 Chemistry 9746/02/NYJC J2/08 PX [Turn Over

5 For Examiner's Use 3 Silver chromate(VI), Ag2CrO4 is only sparingly soluble in water. (a) Write an expression for the solubility product, Ksp, of silver chromate(VI). .............................................................................................................................. ..[1] (b) The solubility of silver chromate(VI) in water at 25 oC is 0.0302 g dm-3. For a saturated solution of silver chromate(VI) at 25 oC, calculate (i) the concentration, in mol dm-3, of chromate ions, (ii) the concentration, in mol dm -3, of silver ions, (iii) the value of K sp of silver chromate(VI), stating the units. [4] (c) Will a precipitate form when equal volumes of solutions containing 3 x 10 -3 mol dm-3 silver nitrate and 5 x 10 -3 mol dm-3 of potassium chromate (VI) are mixed together? Explain your answer, with the aid of relevant calculations. [2] [Total: 7] H2 Chemistry 9746/02/NYJC J2/08 PX [Turn Over

6 For Examiner's Use 4(a) (i) Write a balanced equation for the reaction of heat on calcium nitrate. ....................................................................................................................... (ii) Explain, with the help of equations in cluding state symbols, what happens when a small amount of water is added initially to the white solid obtained after heating in (a)(i