Chemistry · Oct / Nov 2024 · Paper 62 · Question 2
0620
As printed in the paper
The question as text
A student investigates the rate of the reaction between aqueous iron(III) nitrate and aqueous sodium thiosulfate. The student does ve experiments using the apparatus shown in Fig. 2.1. printed sheet printed text aqueous sodium thiosulfate eye 50 cm3 of aqueous iron(III) nitrate 100 cm3 beaker Fig. 2.1 Experiment 1 ● Use a 50 cm3 measuring cylinder to pour 50 cm3 of aqueous iron(III) nitrate into a 100 cm3 beaker. ● Stand the beaker on the text of the printed sheet as shown in Fig. 2.1. ● Use a 25 cm3 measuring cylinder to pour 15.0 cm3 of aqueous sodium thiosulfate into the beaker. At the same time start a stop-watch. ● Stir the contents of the beaker. ● Look down from above the beaker. When the text on the printed sheet becomes visible, stop the stop-watch and record the time in seconds to the nearest whole number. ● Rinse the beaker with distilled water. Experiment 2 ● Repeat Experiment 1, using 10.0 cm3 of aqueous sodium thiosulfate instead of 15.0 cm3. Experiment 3 ● Repeat Experiment 1, using 7.0 cm3 of aqueous sodium thiosulfate instead of 15.0 cm3. Experiment 4 ● Repeat Experiment 1, using 6.0 cm3 of aqueous sodium thiosulfate instead of 15.0 cm3. Experiment 5 ● Repeat Experiment 1, using 5.0 cm3 of aqueous sodium thiosulfate instead of 15.0 cm3.
Read automatically from the paper; the printed page above is exact.
Show the answer and mark scheme
2(a)[3]
M1 all five volumes of aqueous sodium thiosulfate recorded correctly (15.0, 10.0, 7.0, 6.0, 5.0)
M2 all five times recorded correctly (24, 51, 63, 98, 118)
M3 all times recorded in seconds only
2(b)[4]
M1 y-axis scale is linear AND points extend over halfway up scale
M2 and M3 all points plotted correctly
M4 best-fit line
2(c)[1]
to mix the reactants / solutions
OR
so that concentration(s) are uniform throughout the mixture
2(d)[1]
Experiment 1
2(e)[3]
M1 working shown at 12.5 cm3 on graph
M2 correct value from graph
M3 units given as s
2(f)(i)[1]
burette is more accurate (than a measuring cylinder)
2(f)(ii)[1]
volume is not the same in each run / volume is not 25 cm3
2(f)(iii)[1]
repeat AND compare / repeat AND look for/exclude anomalies / repeat AND compare curve shape
2(g)[2]
M1 times longer
M2 greater depth of liquid
2(h)[1]
(measure) temperature before AND after (the reaction)
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