Zadanie 1a
Determine the mass of sodium thiosulfate pentahydrate, Na2S2O3 ⋅ 5 H2O, needed to prepare 250.0 cm3 of a 0.2000 mol dm−3 solution.
- Materiał graficzny
Chemistry HL Paper 1B, May 2025, TZ1
Zadania wzorowane na pytaniach z tego arkusza: te same umiejętności, format i punktacja, inne dane i kontekst. Treści arkusza IB nie publikujemy.
W bazie 19 zadań z tego arkusza, razem 35 punktów, każde z kluczem i schematem punktowania. Najwięcej zadań sprawdza: Molar concentration of solutions (8), Units, uncertainties and graphs (8), Colour of transition metal complexes (7).
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Dodaj cały arkusz do zestawuZadanie 1b
Explain how the 0.2000 mol dm−3 solution is prepared in a volumetric flask from the weighed solid.
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Zadanie 1c
Suggest how to prepare 100.0 cm3 of a 0.05000 mol dm−3 sodium thiosulfate solution from the 0.2000 mol dm−3 solution.
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Zadanie 1d
The student's results are shown below. Each time was measured to ± 0.1 s. Rather than diluting the stock solution, the student prepared every solution separately, weighing the required mass of the solid on a balance reading to ± 0.01 g and making each one up…
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Zadanie 1e
The average times were plotted against concentration. Draw a curve of best fit through the points on the graph.
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Zadanie 1f
A second student repeated the experiment with the same five solutions and the same apparatus and obtained the following times. Suggest two reasons why these times differ significantly from the average times obtained by the first student.
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Zadanie 1g
State one safety concern arising from a product of this reaction, and a precaution that should be taken because of it.
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Zadanie 2a
Suggest a sequence of experimental steps that would give a pure sample of each of the three components.
Zadanie 2b
The student recorded the following masses. Calculate the percentage by mass of iron and of calcium carbonate in the mixture.
- Tabela do uzupełnienia
Zadanie 2c
The three percentages in 2b add up to more than 100 %. Suggest an error that would explain this result and how it could be reduced or eliminated.
Zadanie 2d
The results did not support the student's hypothesis. Suggest what the student overlooked when forming the hypothesis.
Zadanie 2e
In a separate experiment, the students needed to separate a mixture of two miscible liquids, ethanol and pentan-1-ol. State the most suitable method of separation and the physical property on which it depends.
Zadanie 3a
Draw a line of best fit on the graph, extrapolating it beyond the range of the data.
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Zadanie 3b
State, in mathematical terms, how the absorbance of these solutions depends on their concentration.
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Zadanie 3c
The colorimeter can record either absorbance or percentage transmittance at a chosen wavelength. Outline why one particular wavelength has to be selected.
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Zadanie 3d
Deduce the equation that relates absorbance to concentration for these solutions, including the numerical value of the constant.
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Zadanie 3e
Estimate the absorbance of a 0.400 mol dm−3 solution of nickel(II) sulfate.
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Zadanie 3f
Predict the difference, if any, between the absorbance of the 0.400 mol dm−3 solution read from the extrapolated line and the value calculated from the equation in 3d.
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Zadanie 3g
Nickel(II) sulfate solution is green. Deduce the most suitable wavelength for this colorimetry, using section 15 of the data booklet.
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