Zadanie 1a
Deduce the oxidation state of chlorine in each of the three chlorine-containing species in the equation. Cl2: HOCl: Cl−:
Chemistry HL Paper 1B, specimen 2025
Zadania wzorowane na pytaniach z tego arkusza: te same umiejętności, format i punktacja, inne dane i kontekst. Treści arkusza IB nie publikujemy.
W bazie 17 zadań z tego arkusza, razem 35 punktów, każde z kluczem i schematem punktowania. Najwięcej zadań sprawdza: Units, uncertainties and graphs (7), Le Chatelier's principle (4), Experimental techniques and apparatus (3).
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Dodaj cały arkusz do zestawuZadanie 1b
The pool operators add sodium carbonate to the water to raise its pH. Explain why a larger proportion of the dissolved chlorine reacts with water after the sodium carbonate has been added.
Zadanie 1c
A student writing a report on chlorine as a disinfectant collects, from several websites and reference books, values for how much chlorine dissolves in pure water at various temperatures. (i) Identify one difficulty in comparing the solubility values from…
- Tabela do uzupełnienia
Zadanie 1d
Most pools, including this lido, are dosed with sodium hypochlorite solution, NaOCl(aq), instead of chlorine gas. Suggest why pool operators avoid dosing the water with chlorine gas itself.
Zadanie 1e
Hypochlorous acid is a weak acid. In water it is in equilibrium with its conjugate base, the hypochlorite ion, OCl−, which kills microorganisms far less effectively than the acid molecule does. The graph shows what percentage of the dissolved chlorine…
- Materiał graficzny
Zadanie 1f
Bathers release nitrogen-containing compounds, including ammonia, into the pool water. Ammonia reacts with hypochlorous acid to form chloramines. (i) Deduce an equation for the reaction of ammonia with hypochlorous acid that forms trichloramine,…
- Materiał graficzny
Zadanie 1g
Some users have asked for the water to be heated in winter. Suggest two reasons why leaving the water unheated is the better choice for the environment.
Zadanie 2a
Identify two controlled variables in this investigation.
- Materiał graficzny
Zadanie 2b
The student measures the hydrogensulfite concentration by titrating samples against a standard iodine solution, with starch as the indicator. Every three days, 25.00 cm3 of cordial is withdrawn from each flask, diluted to 250.0 cm3 with…
- Materiał graficzny
Zadanie 2c
The following burette readings are recorded in one of the titrations. Final burette reading = 26.15 ± 0.05 cm3 Initial burette reading = 1.15 ± 0.05 cm3 Calculate the percentage uncertainty in the titre volume.
- Materiał graficzny
Zadanie 2d
The student's results are plotted below. (i) Calculate the average rate at which the hydrogensulfite concentration in the 24 h flask decreased over the 12 days. Include units in your answer. (ii) Before starting, the student wrote this hypothesis: "The longer…
- Materiał graficzny
Zadanie 2e
Suggest one way of extending the investigation so that it could lead to additional advice on storing cordial.
- Materiał graficzny
Zadanie 3a
By drawing a suitable line on the graph, determine the rate at which carbon dioxide is released at the start of Experiment 1. Give your answer in cm3 s−1.
- Materiał graficzny
Zadanie 3b
Estimate how long after the start of the experiment the piston would first move if a total mass of 750 g were loaded on it.
- Materiał graficzny
Zadanie 3c
Suggest two reasons why less carbon dioxide is collected in the syringe when a greater mass rests on the piston.
- Materiał graficzny
Zadanie 3d
Use the volumes collected at 120 s in Experiment 1 and Experiment 3 to calculate by what percentage the final volume of carbon dioxide falls for each 100 g added to the piston.
- Materiał graficzny
Zadanie 3e
Sketch how the combined mass of the flask, the syringe and their contents would change with time during Experiment 1, and give a reason for the shape of your sketch. Label the axes 'Total mass' and 'Time'.
- Materiał graficzny