Chemistry • Year 11 • Module 1 • Lesson 5
IQ1 Consolidation — Classification and Separation
Lock in the vocabulary, steps, and decision rules for gravimetric analysis and the five separation techniques before tackling harder questions.
1. Term–definition match
The definitions below are shuffled. In the right-hand column write the matching term from this list: gravimetric analysis, precipitation, precipitate, stoichiometry, filtration, crystallisation, simple distillation, fractional distillation, chromatography, co-precipitation. 10 marks (1 each)
| # | Definition | Matching term |
|---|---|---|
| 1.1 | A quantitative technique where the amount of a substance is determined by measuring the mass of a dried precipitate formed in a chemical reaction. | |
| 1.2 | The formation of an insoluble solid when two solutions are mixed and a substance that is insoluble in the solvent is produced. | |
| 1.3 | An insoluble solid formed from a reaction in solution, which can be separated from the solution by filtration. | |
| 1.4 | The quantitative relationship between reactants and products in a chemical reaction, based on the balanced equation. | |
| 1.5 | A separation technique that exploits differences in particle size to separate an insoluble solid from a liquid. | |
| 1.6 | A separation technique that exploits the change in solubility with temperature to obtain a pure solid from solution. | |
| 1.7 | A separation technique for separating a liquid from a non-volatile dissolved solid, or two liquids with a large boiling point difference, by vaporising and condensing one component. | |
| 1.8 | A separation technique that uses a fractionating column to separate two miscible liquids with similar boiling points. | |
| 1.9 | A separation technique that exploits differences in the affinity of substances for a stationary phase and a mobile phase to separate dissolved components. | |
| 1.10 | An error in gravimetric analysis where impurity ions precipitate together with the target ion, adding unexpected mass to the precipitate. |
2. True or false — with correction
Circle T or F for each statement. If the statement is false, write the corrected version on the line below it. 12 marks (1 T/F + 1 correction each)
2.1 In gravimetric analysis, the precipitating reagent should be added in exactly stoichiometric amounts to avoid excess. T / F
2.2 Filtration can be used to separate a dissolved salt from a solution because filter paper traps all particles. T / F
2.3 In a gravimetric analysis, the precipitate must be dried to constant mass before weighing to remove all residual moisture. T / F
2.4 Chromatography can separate a mixture of dissolved compounds whose boiling points differ by only a few degrees. T / F
2.5 Gravimetric analysis measures the mass of a dried, pure precipitate and uses stoichiometry to calculate the original amount of the target substance. T / F
2.6 Simple distillation and fractional distillation both exploit differences in boiling point, but fractional distillation is used when boiling points are very close together. T / F
3. Fill-in-the-blank paragraph
Use the word bank to complete the passage. Each word or phrase is used once. 8 marks (1 per blank)
Word bank:
ashless · boiling point · constant mass · excess · filtration · insoluble · precipitate · stoichiometry
In gravimetric analysis, a ___________ is formed by adding ___________ precipitating reagent to ensure all the target ions react. The resulting solid is separated from the solution by ___________, using ___________ filter paper so that no extra mass is added when the paper is later ignited. The precipitate is washed with distilled water to remove soluble impurities, then dried in an oven to ___________ to ensure all moisture is removed. The dried mass is used with ___________ to calculate the original amount of the target substance. The choice of this technique relies on the fact that the target ion forms an ___________ solid with the reagent. In contrast, choosing simple distillation requires a large difference in ___________ between the components being separated.
4. Sequence the steps — gravimetric analysis procedure
The steps below are scrambled. Write the correct order number (1–7) in the “Order” column. 7 marks (1 per correctly placed step)
| Order | Step (scrambled) |
|---|---|
| Weigh the dried precipitate on an analytical balance. | |
| Add an excess of the precipitating reagent to the aqueous sample solution. | |
| Use stoichiometry to calculate the mass/amount of the original target substance. | |
| Wash the collected precipitate with distilled water to remove soluble impurities. | |
| Dissolve the solid sample in water (or prepare the aqueous solution of the unknown). | |
| Dry the precipitate to constant mass in an oven or desiccator. | |
| Filter the precipitate using ashless filter paper to separate it from the solution. |
5. Build a concept map — separation technique selection
Draw labelled arrows between the six terms below to show how they relate to each other. Each arrow must carry a linking phrase (e.g. “is used when”, “exploits”, “produces”). Aim for at least 6 labelled arrows. 6 marks (1 per valid labelled arrow)
Supplied terms: gravimetric analysis · filtration · precipitation · particle size · insoluble precipitate · stoichiometry.
Q1 — Term–definition match
1.1 gravimetric analysis • 1.2 precipitation • 1.3 precipitate • 1.4 stoichiometry • 1.5 filtration • 1.6 crystallisation • 1.7 simple distillation • 1.8 fractional distillation • 1.9 chromatography • 1.10 co-precipitation.
Q2 — True / false with correction
2.1 False. The precipitating reagent must be added in excess, not stoichiometric amounts. Excess ensures that all target ions are forced to precipitate; insufficient reagent leaves some ions in solution, leading to an underestimate.
2.2 False. Filtration cannot separate a dissolved salt from solution. Dissolved particles are too small to be trapped by filter paper and pass through in the filtrate. Filtration separates insoluble solids from liquids.
2.3 True.
2.4 False. Chromatography separates dissolved compounds that have different affinities for the stationary and mobile phases. Close boiling points are exploited by fractional distillation, not chromatography.
2.5 True.
2.6 True.
Q3 — Cloze paragraph
In order: precipitate / excess / filtration / ashless / constant mass / stoichiometry / insoluble / boiling point.
Q4 — Sequence the steps
Correct order: 1 Dissolve sample in water → 2 Add excess precipitating reagent → 3 Filter precipitate (ashless paper) → 4 Wash precipitate with distilled water → 5 Dry to constant mass → 6 Weigh precipitate → 7 Use stoichiometry to calculate result.
Q5 — Sample concept map
Correct maps should include arrows such as:
- gravimetric analysis — uses → precipitation
- precipitation — forms → insoluble precipitate
- insoluble precipitate — is separated by → filtration
- filtration — exploits → particle size
- gravimetric analysis — uses → stoichiometry
- stoichiometry — calculates result from → insoluble precipitate
Award 1 mark per valid labelled arrow (minimum 6, maximum 6 marked).