IJC H2 Chem 2012 Prelim P2 Soln

2 PRELIM 2  INNOVA 9647/02/2012 [Turn over For Examiner’s Use (c) Write a plan which will allow an identification of the three solutions to be made. You may use the reagents and apparatus normally found in a school or college laboratory. However, you are not provided with an indicator. In your plan you should give essential details, including quantities, of the identification procedure. To insert lines………………………………………………………………………………[6] Procedure 1.By using a 50cm 3/100cm3 measuring cylinder, place 50cm 3 of NaOH, into the dry polystyrene cup provided supported with a glass beaker. 2. Measure and note the initial temperature of NaOH solution using a 1.0 oC interval thermometer. 3.By using a second 50cm 3/100cm3 measuring cylinder (otherwise must mention washing & drying of the previous m.cyliner), measure 25 cm3 of acidic solution X. 4.Note the initial temperature of solution X. (both initial temp taken to find the average initial temp) 5.Add solution X to the cup in step 1. 6.Stir gently with a thermometer and note the highest temperature reached 7. Repeat the experiment (steps 1 to 6) with solutions Y and Z, using different measuring cylinders or mentioned in procedure measuring cylinder must be dry. Record all your readings (temperature) in an appropriate table. or a sample table is drawn. (d) Explain how you can make use of your experimental data to identify the three solutions. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ………………………………………………………………………………………[2] Feasibility of the identification depends on volume used in the experiment. Must use results obtained (either ∆H neu calculated or ∆T) . When V NaOH should be greater than VHCl:

3 PRELIM 2  INNOVA 9647/02/2012 [Turn over For Examiner’s Use -using enthalpy change of neutralisation calculated: Due to partial dissociation of CH 3COOH, some heat is absorbed to dissociate the weak acid. Thus, the ∆Hneu is less exothermic/smaller ∆ T than HCl of same concentration. In this experiment, more no. of moles of water produced with 2.0 mol dm -3 HCl used is than when 1.0 mol dm -3 HCl used. Thus, the one with a larger/twice the ∆ T is the one using solution 2.0 m