Chemistry · May / June 2021 · Paper 62 · Question 2
0620
As printed in the paper
The question as text
A student investigated the volume of gas made when sodium carbonate reacts with dilute hydrochloric acid. Five experiments were carried out using the apparatus shown. trough water clamp inverted 100 cm3 measuring cylinder boiling tube bung rubber delivery tube Experiment 1 ● Using a measuring cylinder, 16 cm3 of dilute hydrochloric acid was poured into a boiling tube. ● The apparatus was set up as shown in the diagram. ● The bung was removed from the boiling tube. ● 2.5 g of sodium carbonate was added to the boiling tube and the bung was immediately replaced. ● When no more gas was being collected, the volume of gas in the measuring cylinder was m Experiment 2 ● Experiment 1 was repeated using 14 cm3 of dilute hydrochloric acid instead of 16 cm3. Experiment 3 ● Experiment 2 was repeated using 12 cm3 of dilute hydrochloric acid instead of 14 cm3. Experiment 4 ● Experiment 3 was repeated using 10 cm3 of dilute hydrochloric acid instead of 12 cm3. Experiment 5 ● Experiment 4 was repeated using 6 cm3 of dilute hydrochloric acid instead of 10 cm3.
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Show the answer and mark scheme
2(a)[3]
all volumes of dilute hydrochloric acid correct (16, 14, 12, 10, 6)
all volumes recorded correctly, 4 correct scores 1
(56, 49, 44, 37, 26)
2(b)[4]
suitable scale for y-axis
plotting – all 5 correct scores 2, 4 correct scores 1
line drawn is a straight line of best fit
2(c)(i)[2]
correct reading from graph (usually 29 cm3)
working shown on graph
2(c)(ii)[1]
answer to (c)(i) ÷ 7
2(d)(i)[1]
gas escapes before bung is replaced /so that gas does not escape
2(d)(ii)[2]
either
place one reagent in tube inside boiling tube / flasktip / shake tube to start reactionOR
use a divided flasktip flask to start reaction2(e)[1]
more accurate
2(f)[2]
line drawn is below plotted line
volumes are half of the values of plotted line
Tests on solid G
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