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21 exam-style questions with model answers, plus 28 quick multi-choice questions — every question on the site for this standard, grouped by the 7 pages of notes they come from.
Write a full answer before you reveal the model one — that comparison is where the marks come from. Every block links back to the notes that teach it.
Explain the difference between primary and secondary data in this standard, giving one example of each.
A student writes in their results table: "Test 1: NaOH added — Cu2+ present. Test 2: BaCl2 added — sulfate present." Explain why this record would not meet the requirements of the standard, and rewrite it so that it would.
Justify why a qualitative analysis report that identifies a species correctly can still fail to reach Excellence, and explain what the use of secondary data adds to an identification.
Predict whether a precipitate would form when each of the following pairs of solutions are mixed, and name any precipitate: (a) sodium carbonate and calcium chloride, (b) potassium nitrate and sodium sulfate.
Explain why a solution must be acidified with dilute nitric acid before silver nitrate is added in a test for chloride ions, and write equations for the changes involved.
A student adds barium chloride to a sample and obtains a white precipitate, concluding that sulfate is present. Justify whether this conclusion is secure, using the solubility rules, and describe the minimum additional evidence required.
A solution gives a pale blue precipitate with sodium hydroxide which does not dissolve in excess. With ammonia, the precipitate dissolves to give a deep blue solution. Identify the cation and state the two observations that identify it.
Explain how the tests with sodium hydroxide and ammonia distinguish Zn2+ from Al3+, and write equations for all the changes that occur with each ion.
Justify, using chemical principles, why ammonia solution first produces a precipitate and then dissolves it when added to a copper(II) solution, and explain what would be observed if concentrated ammonia were added all at once instead.
Describe the test for carbonate ions, stating the reagent, the observation, and how the gas is confirmed.
Explain how a student would distinguish between chloride, bromide and iodide ions in three separate samples, writing equations for the changes.
A student tests a sample for sulfate by adding barium chloride, obtains a white precipitate, and reports sulfate present. They then test a second portion for chloride by adding silver nitrate to the same acidified solution and obtain a white precipitate, reporting chloride present. Evaluate the reliability of both conclusions and justify a corrected procedure.
Describe a chemical test that would distinguish ethanol from ethanoic acid, stating the reagent and the observation for each.
Explain why a haloalkane does not give a precipitate when silver nitrate is added directly, and describe the procedure that does identify the halogen present, with equations.
A student tests an unknown liquid with bromine water on a sunny bench and observes decolourisation, concluding an alkene is present. Evaluate this conclusion, justify what chemical principle makes it unsafe, and describe how the test should be performed and confirmed.
A student identifies nitrate ions in a water sample taken from a drain in a dairy farming area. Describe the significance of this species for people and the environment.
Explain the significance of identifying lead ions, Pb2+, in water collected from a roof-fed water tank on an older house.
A student identifies both Ca2+ and SO42− in a water sample from a bore in a limestone region. Discuss the significance of these species, considering more than one perspective.
A sample is found to contain Fe3+ and SO42−. State the formula and name of the compound present, and explain how you determined the formula.
Explain why recording negative results is important in a qualitative analysis report, using an example.
A student's report identifies Cu2+ and Cl− correctly and includes all the required equations, but the marker awards Merit rather than Excellence. Justify what is most likely missing, and explain what the student should have written.