Chemistry · May / June 2020 · Paper 62 · Question 2
0620
As printed in the paper
The question as text
A student investigated the temperature change when magnesium ribbon reacts with dilute sulfuric acid. Five experiments were done. Experiment 1 ● Using a measuring cylinder, 20 cm3 of dilute sulfuric acid were poured into a boiling tube. ● A thermometer was used to measure the initial temperature of the acid. ● A 1 cm length of magnesium ribbon was added to the acid in the boiling tube. ● The acid and magnesium ribbon in the boiling tube were stirred continuously using a thermometer. ● The highest temperature reached by the mixture was measured. ● The boiling tube was rinsed out with distilled water. Experiment 2 ● Experiment 1 was repeated using a 2 cm length of magnesium ribbon instead of the 1 cm length. Experiment 3 ● Experiment 1 was repeated using a 3 cm length of magnesium ribbon instead of the 1 cm length. Experiment 4 ● Experiment 1 was repeated using a 5 cm length of magnesium ribbon instead of the 1 cm length. Experiment 5 ● Experiment 1 was repeated using a 6 cm length of magnesium ribbon instead of the 1 cm length.
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Show the answer and mark scheme
2(a)[4]
lengths completed correctly (1, 2, 3, 5, 6)
10 correct thermometer readings (23 × 5, 24, 26, 29, 36, 40)
All temperature increases worked out correctly (1, 3, 6, 13, 17)
2(b)[1]
5
2(c)[5]
scale has one big square = 5
all five points plotted correctly
best fit line through points
which passes within half a small square of (0, 0)
2(d)[1]
there is no reaction (with no magnesium)
2(e)[3]
working shown on graph
correct reading
units of °C shown
2(f)(i)[1]
(polystyrene is a better) insulator
2(f)(ii)[1]
sketch line starts at same point as plotted line for 0 cm magnesium and then is above plotted line at all non-zero lengths of magnesium.
2(g)(i)[1]
more accurate
2(g)(ii)[1]
slower
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