Chemistry · Oct / Nov 2024 · Paper 61 · Question 2
0620
As printed in the paper
The question as text
A student investigates the reaction between aqueous magnesium sulfate and aqueous barium nitrate. A precipitate of barium sulfate forms in the reaction. The student does eight experiments. Experiment 1 ● Fill a burette with aqueous magnesium sulfate. Run some of the aqueous magnesium sulfate out of the burette so that the level of the aqueous magnesium sulfate is on the burette scale. ● Fill a second burette with aqueous barium nitrate. Run some of the aqueous barium nitrate out of the burette so that the level of the aqueous barium nitrate is on the burette scale. ● Add 4.0 cm3 of aqueous magnesium sulfate from the first burette into a 10 cm3 measuring cylinder. ● Add 1.0 cm3 of aqueous barium nitrate from the second burette into the same measuring cylinder. ● Place a stopper in the top of the measuring cylinder and invert the measuring cylinder several times. ● Leave the measuring cylinder to stand for 15 minutes. ● Record the level of the precipitate on the measuring cylinder scale. ● Rinse the measuring cylinder with distilled water. Experiment 2 ● Repeat Experiment 1 using 1.5 cm3 of aqueous barium nitrate instead of 1.0 cm3. Experiment 3 ● Repeat Experiment 1 using 2.5 cm3 of aqueous barium nitrate instead of 1.0 cm3. Experiment 4 ● Repeat Experiment 1 using 3.0 cm3 of aqueous barium nitrate instead of 1.0 cm3. Experiment 5 ● Repeat Experiment 1 using 3.5 cm3 of aqueous barium nitrate instead of 1.0 cm3. Experiment 6 ● Repeat Experiment 1 using 4.5 cm3 of aqueous barium nitrate instead of 1.0 cm3. Experiment 7 ● Repeat Experiment 1 using 5.0 cm3 of aqueous barium nitrate instead of 1.0 cm3. Experiment 8 ● Repeat Experiment 1 using 5.5 cm3 of aqueous barium nitrate instead of 1.0 cm3.
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2(a)[4]
M1 all volumes AND precipitate levels are recorded to 1 dp
M2 all volumes of aqueous magnesium sulfate (4.0) and aqueous barium nitrate are correct ((1.0), 1.5, 2.5, 3.0, 3.5, 4.5, 5.0, 5.5)
M3 and M4 all 7 precipitate levels correct (1.8, 3.0, 3.6, 4.2, 4.6, 4.6, 4.6)
2(b)[5]
M1 linear scale for y-axis
M2 and M3 all 8 points plotted correctly
M4 ruler drawn straight line through first five points AND line extends to the origin
M5 ruler drawn straight line through last three points AND lines extend so that they meet / cross
2(c)[2]
M1 working on graph to show reading at 2.8 cm3 of barium nitrate
M2 correct reading
2(d)[2]
M1 4.6 (cm3)
M2 all magnesium sulfate has reacted
2(e)[2]
M1 graph line starts at (0,0) and is below results line
M2 sketch line continues to 6 cm3 with positive gradient and does not level off and is approximately half precipitate level of original line
2(f)[1]
to mix the reactants / solutions
OR
so that concentration(s) are uniform throughout the mixture
2(g)[1]
so that the precipitate settles out / so that the precipitate falls to the bottom
2(h)(i)[1]
(a burette is) more accurate (than a measuring cylinder)
2(h)(ii)[1]
the volumes are not fixed volume / not the same in each run
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