JJC H2 Chem 2012 Prelim P2 QP

q CANDIDATE NAME CLASS JURONG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 EXAM INDEX NUMBER CHEMISTRY 9647/02 Paper 2 Structured Questions 12 September 2012 2 hours Candidates answer on 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 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. Do not write anything on the Data Booklet. 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 Total This document consists of 16 printed pages. [Turn over

2 Jurong Junior College 9647/02/Prelim 2012 [Turn over 1. Planning (P) You are to plan an investigation into the thermal decomposition of caesium nitrate, CsNO3. You may make use the following data when planning your investigation. Data: Group I element cation Ionic radius / nm lithium Li+ 0.060 sodium Na+ 0.095 potassium K+ 0.133 rubidium Rb+ 0.148 caesium Cs+ 0.176 Equation for the thermal decomposition of lithium nitrate and sodium nitrate are given below: 1. 4LiNO3(s) ® 2Li2O(s) + 4NO2(g) + O2(g) 2. 2NaNO3(s) ® 2NaNO2(s) + O2(g) Nitrogen dioxide gas Oxygen gas NO2 O2 brown in colour colourless soluble in water almost insoluble in water poisonous powerful oxidant 1 mol of any gas occupies a volume of approximately 24 dm 3 at room temperature and atmospheric pressure. Ar: Cs, 133; N, 14.0; O, 16.0 (a) Predict which of the equations below will represent the thermal decomposition of caesium nitrate. Place a tick against the equation of your choice. 4CsNO3(s) ® 2Cs2O(s) + 4NO2(g) + O2(g) 2CsNO3(s) ® 2CsNO2(s) + O2(g) Use the data provided to explain your prediction. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. [2]

3 Jurong Junior College 9647/02/Prelim 2012 [Turn over 1. (b) You are to plan an experiment in which · caesium nitrate is heated · gas is collected · the volume of gas collected is measured · the experimental results are used to confirm or reject your prediction (i) Draw a diagram of the apparatus you would use in this experiment. Your apparatus should use only standard items found in college laboratory. Label each piece of apparatus used, indicating its size or capacity and state the gas or gases collected on your diagram. [3] (ii) Calculate the volume of gas you would expect to collect at room temperature and atmospheric pressure if 1 mol of caesium nitrate completely decomposed according to your predicted equation in (a). [1]

4 Jurong Junior College 9647/02/Prelim 2012 [Turn over 1. (c) Use your answer to (b)(ii) and the capacity of the apparatus selected in (b)(i) to calculate the maximum mass of CsNO3 that can be used in your experiment. [1] (d) Outline, in a series of numbered step s, the method to be used in the experiment. Make certain that the steps you describe are in the correct order. You need not explain how the apparatus is assembled. Indicate clearly how you will know when decomposition is complete. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. [3]

5 Jurong Junior College 9647/02/Prelim 2012 [Turn over 1. (e) What should be done when decomposition is complete to ensure that the volume of the gas measured in the apparatus is the “correct” volume? ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. [1] (f) Identify a risk present in the method you have described and suggest how you would minimise this risk. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................................................. ............................................................................................