JJC H2 Chem 2013 Prelim P2 QP

[Turn over JURONG JUNIOR COLLEGE 2013 JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS EXAM INDEX NUMBER CHEMISTRY 9647/02 Paper 2 Structured Questions 30 August 2013 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and exam index number 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 Total This document consists of 18 printed pages and 2 blank pages. 596

2 © Jurong Junior College 9647/02/PRELIM/2013 1 Planning (P) For Examiner’s Use Solubility of a substance is the maximum mass of the substance dissolved in a given volume of a particular solvent to give a saturated solution at a specified temperature. The units of solubility is grams per hundred grams of water (i.e. g /100 g water). When solid potassium nitrate is dissolved in water, the temperature of solution decreases. KNO3(s)  K+(aq) + NO3 –(aq) To investigate how the solubility of potassium nitrate varies with temperature, a student demonstrated the experiment, at 30 °C, as follows. The solid was added into 50 cm 3 of water in a small beaker until a saturated solution at 30 °C is obtained. The mixture was filtered and the filtrate was collected in a crucible. The filtrate in the crucible was heated to evaporate off the water and the mass of potassium nitrate dissolved in 50 cm 3 of water was determined. (a) Predict, in the form of a sketch graph, how the solubility of potassium nitrate changes if the solution temperature is increased. Explain your answer. Explanation: ……………………………………………………………………………………...………. ……………………………………………………………………………………...………. ……………………………………………………………………………………...………. ……………………………………………………………………………………...………. [2] (b) State and explain one limitation for heating the solid to dryness. …………………………………………………………………………………...…………. ……………………………………………………………………………………...………. [1] 597

3 © Jurong Junior College 9647/02/PRELIM/2013 [Turn over 1 (c) Consider the brief description of the experiment given on Page 2. The prediction in (a) can be determined by performing a number of experiments. Write a plan for such a series of experiments. In your plan, you should use the same volume of water to dissolve the solid as described on Page 2. Your plan should also ensure that the temperature of each solution is between 30 °C and 70 °C.