Chemistry · Oct / Nov 2021 · Paper 62 · Question 2
0620
As printed in the paper
The question as text
A student investigated the reaction between two different solutions of aqueous sodium carbonate, solution K and solution L, and two different solutions of dilute hydrochloric acid, acid M and acid N. Three experiments were done.
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Show the answer and mark scheme
2(a)[5]
M1 Experiment 1 burette readings completed correctly (31.6 and 8.0)
M2 Experiment 2 burette readings completed correctly (15.9 and 4.1)
M3 Experiment 3 burette readings completed correctly (26.4 and 2.7)
M4 All subtractions to give volume added correct (23.6, 11.8, 23.7)
M5 All readings / volumes are given to 1 dp or better
2(b)[1]
(from) red (to) orange
2(c)[1]
effervescence / fizzing / bubbles
2(d)(i)[2]
M1 greater volume used in experiment 1 / smaller volume used in experiment 2
M2 twice as much in experiment 1 / half as much in experiment 2
2(d)(ii)[1]
solution M is more concentrated than solution N
2(e)[1]
47.4
2(f)[1]
to clean / to remove residue from previous experiment
2(g)[2]
M1 rinse with solution L
M2 to remove water / avoid diluting solution L / avoid changing concentration (of L)
2(h)[1]
to see colour change clearly / easily / accurately / better
2(i)[1]
repeat the experiments
and compare the results
2(j)[2]
M1 source of error: measuring cylinder / error in volume of solution M
M2 improvement: use a pipette
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