ASRJC N2017, 2019, 2020, 2021 Planning Solutions

Solution to N2017/P4/Q2c Part (i) Since the question stated that “The procedure you followed in 2(a)(i) can be modified”, the table below shows the modifications that are made from the procedures in 2(a)(i) of the original exam question to study the effect of temperature on rate of decomposition. You may take reference of the original procedure from Experiment 21 that you have done in JC2. You will only need to give the answer in the right-hand side column. Original procedure in Expt 2(a) Planning Procedure to answer 2(c)(i) 1. Fill the burette with FA 3 (KMnO4) Fill the burette with KMnO4. 2. Using a measuring cylinder, add 100.0 cm3 of FA 4 to the conical flask labelled reaction mixture. Using a measuring cylinder, add 100.0 cm3 of H2O2 to the conical flask labelled “reaction mixture”. Place this conical flask labelled “reaction mixture” into a thermostatically controlled water bath maintained at 30oC. Insert a thermometer into the reaction mixture. Allow the temperature of the reaction mixture to equilibrate to within 1°C of the water bath. Record the temperature of the reaction mixture. 3. Using a measuring cylinder, add 2.0 cm3 of FA 2 (iron(III) nitrate, Fe(NO3)3, is an effective catalyst) to the same conical flask. Start the stopwatch and swirl the mixture thoroughly to mix its content. Note: in 2022 JC2 experiment 21, the volume of FA2 used is 4.0 cm3. Using a scalpel, cut a small piece of liver with dimension 1cm x 1cm x 1cm. Add the small piece of liver to the same conical flask. Start the stopwatch and swirl the mixture thoroughly to mix its content. 4. Using a measuring cylinder, add 50.0 cm3 of 0.2 mol dm-3 sulfuric acid to a second conical flask. Using a measuring cylinder, add 50.0 cm3 of 0.2 mol dm-3 sulfuric acid to a second conical flask. 5. Transfer a 10.0 cm3 aliquot (portion) of the reaction mixture to a 10 cm3 measuring cylinder, using a dropping pipette. Transfer a 10.0 cm3 aliquot (portion) of the reaction mixture to a 10 cm3 measuring cylinder, using a dropping pipette. 6. Immediately transfer this aliquot into the second conical flask and vigorously swirl the mixture. Read and record the time of transfer in minutes and seconds, to the nearest second, when the aliquot is added. Immediately transfer this aliquot into the second conical flask and vigorously swirl the mixture. Read and record the time of transfer in minutes and seconds, to the nearest second, when the aliquot is added.

Original procedure in Expt 2(a) Planning Procedure to answer 2(c)(i) 7. Immediately titrate the H2O2 in the second conical flask with FA 3. The end-point is reached when a permanent pale pink colour is obtained. Record the titration results. Immediately titrate the H2O2 in the second conical flask with KMnO4. The end-point is reached when a permanent pale pink colour is obtained. Record the titration results. 8. Wash out the second conical fl