Experimental Techniques and Chemical Analysis

• If you can say which step of the loop a question is standing on, you can always start the answer. Most lost marks in Topic 12 are steps 5 and 6 collapsed into one: writing “copper is present” where the question asked what you would see.
• Five subsections. Fifteen checks in 12.1, four in 12.2, five in 12.3 (three Core, two Supplement), eight in 12.4 and twenty-seven in 12.5 — fifty-nine in total, of which fifty-seven are Core. More than two fifths of the topic is the qualitative analysis tables, which is why they are taught here as a routine and not as a wall to memorise.
• Precipitates are described with two words — a colour and the word precipitate. “Blue solution” and “blue precipitate” are different observations, and only one of them is what happened.
• Nine of these fourteen are a pair of words that sound similar. If you can say the difference between residue and filtrate, precision and accuracy, and a precipitate and a colour change, you have already protected a large block of the marks in this topic.
• Everything in 12.5 answers one of two questions: what would I see? or what does that mean? Decide which one is being asked before you write anything.
• Marks by subsection: 12.1 — 26; 12.2 — 12; 12.3 — 14; 12.4 — 16; 12.5 — 28; practical overlay — 8. Total 104.
• If you have only ten minutes before an exam, spend them on the cation matrix and the six flame colours. They are the densest marks in the topic and the fastest to lose.

• I can name the apparatus used to measure time, temperature, mass and volume, and say which of the seven named items suits a given task.
• I can suggest an advantage and a disadvantage of a method or apparatus for the task in front of me, rather than reciting a universal claim.
• AO3 skill I can read an analogue scale correctly, including to the nearest half-scale division where that is required, and record the value with its unit. This is a practical skill assessed on Paper 5 or Paper 6, on both routes; it is not one of the three numbered 12.1 statements, so it is not counted among the checks below.
• I can describe a solvent, a solute, a solution, a saturated solution, a residue and a filtrate in the exact words the syllabus uses.
• I can describe an acid-base titration that uses a burette, a volumetric pipette and a suitable indicator, and say what each item is for.
• I can describe how the end-point is identified with an indicator, including approaching it dropwise and stopping at the first permanent colour change.
• I can obtain the titre as final reading minus initial reading, and record burette readings consistently.
• I can describe how paper chromatography separates a mixture of soluble coloured substances using a suitable solvent, including a pencil baseline above the solvent.
• I can interpret a simple chromatogram to identify an unknown substance by comparison with known substances run under the same conditions.
• I can interpret a simple chromatogram as pure or impure.
• I can describe how paper chromatography separates a mixture of soluble colourless substances, using a suitable solvent and a locating agent — and I can say what the locating agent does without naming one.
• I can state and use \(R_f = \dfrac{\text{distance travelled by substance}}{\text{distance travelled by solvent}}\), measuring both from the same baseline.
• I can describe and explain separation and purification using a suitable solvent, filtration, crystallisation, simple distillation and fractional distillation.
• I can suggest a suitable technique when I am given information about the substances involved, and justify it from that information.
• I can identify a substance by comparing a measured melting point or boiling point with known values.
• I can assess purity from melting point or boiling point information, using sharpness of the value as the evidence.
• I can describe the test and the exact result for seven anions: carbonate, chloride, bromide, iodide, nitrate, sulfate and sulfite.
• I can describe what aqueous sodium hydroxide and aqueous ammonia do to eight aqueous cations, dropwise and then in excess.
• I can describe the test and the exact result for six gases: ammonia, carbon dioxide, chlorine, hydrogen, oxygen and sulfur dioxide.
• I can give the flame colour for six metal ions: lithium, sodium, potassium, calcium, barium and copper(II).
• I can combine two independent results, each on a fresh sample, to deduce an ion — and say when the evidence is not yet enough.

Why a fresh sample every time. Reagents do not politely wait their turn. Add dilute nitric acid and silver nitrate to a solution, then add sodium hydroxide to the same tube, and you are no longer testing the original substance — you are testing whatever the first test left behind. Two specific traps: a solution acidified with hydrochloric acid now contains chloride ions, so a later silver nitrate test gives a white precipitate whatever the sample was; and a solution to which sodium hydroxide has been added will produce ammonia from any ammonium ion present, which can be mistaken for a positive nitrate test if aluminium is added later. Fresh portion, clean tube, every time.

• 1. Mass and weight Fix A balance measures mass, in grams. Weight is a force. In practical chemistry you record mass, and “weigh the solid” is laboratory shorthand for “find its mass”. Write mass in the answer.
• 2. Fixed volume and variable volume Fix A volumetric pipette transfers one fixed volume it was made for. A burette delivers any volume you choose, and tells you which volume that was. A measuring cylinder also gives a variable volume, but with coarser graduations. Match the apparatus to which of these the task needs.
• 3. A reading and a volume delivered Fix A burette reading is a position on a scale. The volume delivered is final reading minus initial reading. Even when the burette starts at \(0.00\ \mathrm{cm^3}\), write the subtraction — that is the habit that stops you quoting the final reading as the titre when it starts somewhere else.
• 4. Precision and accuracy Fix Accuracy is closeness to the true value. Precision is how finely the instrument resolves and how closely repeats agree. A balance reading to \(0.001\ \mathrm{g}\) that is not zeroed is precise and inaccurate. Do not use the words as synonyms; questions ask about one or the other.
• 5. Residue and filtrate Fix The filtrate is the liquid or solution that has passed through the filter. The residue is what remains after a process — and that process may be filtration, evaporation or distillation, not only filtration. Never define residue as “the solid on the filter paper”; that is one example of a residue, not the meaning of the word.
• 6. Solute and solvent Fix The solute is dissolved; the solvent does the dissolving. In salt water the solute is salt and the solvent is water. Say which is which explicitly — a lot of definition marks are lost by writing the pair the wrong way round under time pressure.
• 7. The end-point and a colour you hoped for Fix The end-point is the first permanent colour change, reached by adding dropwise near the end and swirling. A flash of colour that swirls away is not the end-point. Which colour you are waiting for depends on the indicator you chose and on which solution is in the flask — there is no single universal end-point colour.
• 8. The baseline and the solvent front Fix The baseline is the pencil line where the spots start. The solvent front is how far the solvent reached, marked as soon as the paper comes out of the tank before it evaporates. The solvent must start below the baseline, never above it. Supplement 12.3.4 Extended candidates also measure both \(R_f\) distances from that baseline.
• 9. Spot distance and solvent distance Supplement 12.3.4 Fix \(R_f\) puts the substance distance on top and the solvent distance underneath. Measure the substance distance to the centre of the spot. Getting a value above 1 means you divided the wrong way round or measured from the bottom edge of the paper.
• 10. Identity and purity Fix A melting point that matches a known value supports identity. A melting point that is sharp rather than spread over a range supports purity. They are separate deductions from the same measurement, and a question often asks for only one of them.
• 11. Reagent and observation Fix “Add aqueous silver nitrate” is the reagent; “a cream precipitate forms” is the observation. A full test answer needs both, in that order, and the acidification step where the official test includes one. Naming only the reagent, or only the colour, is half an answer.
• 12. A precipitate and a colour change Fix A precipitate is an insoluble solid appearing in a liquid — the mixture goes cloudy or a solid settles. A colour change is a solution changing colour while staying clear. Sulfite decolourises acidified aqueous potassium manganate(VII); it does not precipitate. Sulfate gives a white precipitate; it is not a colour change.
• 13. Damp litmus and dry litmus Fix The ammonia and chlorine tests both specify damp litmus paper. Dry paper may give no result at all, so “litmus paper” without “damp” can cost the mark. Ammonia turns damp red litmus blue; chlorine bleaches damp litmus paper.
• 14. The dropwise result and the excess result Fix Cation tests have two stages. Add the reagent a few drops at a time and record what forms; then keep adding until the reagent is in excess and record whether the precipitate stays or dissolves. Aluminium and zinc look identical at stage one with sodium hydroxide, and identical again in excess. Only a fresh sample with aqueous ammonia separates them.
• 1. “Use a burette, because it is the most accurate.” Why it fails Precision that nothing in the task depends on is wasted, and here it makes the method slower and no better. Apparatus is chosen for the job, not ranked in order of finesse. Correct Match the apparatus to what the volume is used for, and check its capacity fits the amount. Check Would you use a burette to add \(200\ \mathrm{cm^3}\) of wash water? Four fillings, four chances of error, for a number that appears in no calculation.
• 2. “The burette has an uncertainty of \(\pm 0.05\ \mathrm{cm^3}\).” Why it fails Nothing in the question said so. Uncertainties in this course come from the scale you are shown or from a value the question supplies, not from memory. Correct Read the scale in the diagram, work out what one division is worth, and record the value to a precision that scale supports. Check A diagram shows a measuring cylinder graduated every \(5\ \mathrm{cm^3}\). Quoting “\(\pm 0.5\ \mathrm{cm^3}\)” from memory would contradict the apparatus in front of you.
• 3. “The residue is the solid on the filter paper.” Why it fails That is one example of a residue, not the definition. Defining it that way makes the salt left in an evaporating basin, and the liquid left in a distillation flask, impossible to name. Correct A residue is a substance that remains after evaporation, distillation, filtration or any similar process. Check Sea water is distilled. What is the residue? The dissolved salts left in the flask — and there is no filter anywhere in the apparatus.
• 4. “A saturated solution is one where no more will dissolve.” Why it fails Warm it and more will dissolve, so the statement describes something that changes as soon as the temperature does. Correct A solution containing the maximum concentration of a solute dissolved in the solvent at a specified temperature. Check Why do crystals form when a hot saturated solution cools? Only the full definition, with temperature in it, can answer that.
• 5. “Fill the tank so the solvent covers the spots.” Why it fails The spots dissolve straight into the solvent in the tank instead of being carried up the paper, so nothing separates. Correct The solvent level must be below the pencil baseline. Check A diagram shows the baseline \(5\ \mathrm{mm}\) above the bottom edge and the solvent \(10\ \mathrm{mm}\) deep. Two faults follow from one measurement.
• 6. “Draw the baseline in pen so it is easy to see.” Why it fails Ink dissolves in the solvent and travels up the paper, producing spots of its own and contaminating the chromatogram. Correct Pencil, which does not dissolve, so the line stays where it was drawn and can still be measured from at the end. Check Why is that a problem specifically for interpreting the result? Because extra spots would be counted as substances in the sample.
• 7. “Measure both distances from the bottom of the paper.” Supplement 12.3.4 Why it fails The strip below the baseline was travelled by neither the substance nor the separation, and adding the same length to the top and bottom of a fraction changes its value. Correct Both distances are measured from the pencil baseline, and the substance distance goes to the centre of the spot. Check \(\frac{36}{80} = 0.45\) but \(\frac{48}{92} = 0.52\). The same paper, the same spot, a different answer.
• 8. “My \(R_f\) is \(0.45\) and the data book says \(0.45\), so it is that substance.” Supplement 12.3.4 Why it fails \(R_f\) depends on the solvent and the conditions as well as on the substance. A match between values obtained under different conditions is not evidence. Correct Run a known sample alongside the unknown, on the same paper in the same solvent, and compare the positions directly. Check Two students use the same solvent but let it run different distances. Can they compare? Their \(R_f\) values, yes; their raw distances, no.
• 9. “One spot proves the sample is pure.” Why it fails Two substances that travel the same distance in that solvent would also give one spot. The evidence supports purity; it does not prove it. Correct Give the exam interpretation — one spot means pure — and use “supports” rather than “proves”. Running the sample again in a different solvent tests the conclusion. Check The same caution applies to the sharp melting point: it supports purity, it does not settle it beyond all doubt.
• 10. “Filter the sea water to get pure water.” Why it fails The salts are dissolved, so they pass through the filter paper with the water. Filtration removes insoluble solid only. Correct Simple distillation: the water vaporises, is condensed and collected as the distillate; the salts stay behind as the residue. Check Sea water is filtered and then distilled. Which step removed the salt? Only the second.
• 11. “The residue is what you collect at the end of the distillation.” Why it fails What is collected is the distillate. The residue is what stays behind in the heated flask. Correct Distillate: condensed vapour, in the receiver. Residue: not vaporised, in the flask. Check In a fractional distillation of ethanol and water, which one is the ethanol at the start? The distillate — and the water is the residue until it in turn distils.
• 12. “It melts at \(133\ ^\circ\mathrm{C}\) instead of \(122\ ^\circ\mathrm{C}\), so it is impure.” Why it fails Purity is judged from the sharpness, not the position. A sharp value at the wrong temperature indicates a pure substance that is something else. Correct Two sentences: it melts sharply, so it is pure; the value does not match, so it is not that substance. Check Melts from \(119\) to \(122\ ^\circ\mathrm{C}\), known value \(122\ ^\circ\mathrm{C}\). Impure, and consistent with that substance.
• 13. “Acidify with dilute hydrochloric acid, then add aqueous silver nitrate.” Why it fails The acid adds chloride ions, so a white precipitate forms whatever the sample contained. The result carries no information. Correct Acidify with dilute nitric acid. Nitrate ions give no precipitate with silver nitrate. Check Which acid must be avoided before aqueous barium nitrate? Sulfuric acid — for exactly the same reason.
• 14. “Add sodium hydroxide and aluminium foil and look for ammonia.” Why it fails The official test says warm carefully. Without warming there may be no detectable gas, and the test appears negative when it is not. Correct Add aqueous sodium hydroxide, then aluminium foil; warm carefully; test the gas with damp red litmus paper. Check Which other test in 12.5 needs warming? Ammonium with sodium hydroxide — “ammonia produced on warming”.
• 15. “A white precipitate forms with sodium hydroxide, so it is calcium.” Why it fails Aluminium and zinc also give a white precipitate at that stage. Half the test has been done. Correct Add the reagent to excess and record the second observation. Insoluble in excess points to calcium; soluble points to aluminium or zinc. Check Does the same warning apply to the light blue precipitate? For identification, no — but the excess result is still part of the required answer.
• 16. “Hydrogen relights a glowing splint.” Why it fails Both halves of the pair have been swapped. Hydrogen pops with a lighted splint; oxygen relights a glowing splint. Correct Hydrogen burns, so it needs a flame already present — a lighted splint, and the pop is the small explosion. Oxygen makes other things burn, so it revives a glowing splint. Check A gas does neither. Name two of the six it could be, and how you would tell them apart.
• 17. “It turns red litmus paper blue, so it is ammonia.” Why it fails The official test specifies damp red litmus paper, and dry paper may show nothing at all. Correct Turns damp red litmus paper blue. Check Which other gas test specifies damp paper? Chlorine — it bleaches damp litmus paper.
• 18. “Copper(II) is present.” (as an answer to “state what you would observe”) Why it fails That is an inference offered where an observation was asked for. You cannot see an ion. Correct “A light blue precipitate forms, which dissolves in excess aqueous ammonia to give a dark blue solution.” Check The reverse also fails: “a cream precipitate” is not an answer to “deduce the anion”.
• 19. “Add sodium hydroxide to the tube that already has silver nitrate in it.” Why it fails The tube no longer contains the original substance. Whatever forms may come from the first reagent rather than from the sample. Correct A fresh portion of the original substance in a clean test-tube for every test. Check Why is a solution acidified with hydrochloric acid useless for a later halide test? It now contains chloride ions of its own.
• 20. “Improvement: repeat the experiment to make it more accurate.” Why it fails Repeating reduces the effect of random error by averaging. It does nothing about a systematic error, and the phrase shows the two have been confused. Correct Name the problem, then give a change that addresses it: “gas escaped while the bung was fitted, so use a sealed vessel with the acid added through an inlet”. Check Three titres agreeing closely but all \(1\ \mathrm{cm^3}\) too high. Would a fourth titration help? No.
• 21. “The syllabus names a volumetric flask as apparatus for measuring volume.” Why it fails Statement 12.1.1 names seven items, and a volumetric flask is not one of them: stop-watches, thermometers, balances, burettes, volumetric pipettes, measuring cylinders and gas syringes. Correct A volumetric flask may appear in a method you are given, and you can use it in an answer; it is simply not one of the seven you are required to name. Check Asked to “name the apparatus in 12.1.1 for measuring a fixed volume”, the answer is the volumetric pipette.
• 22. “Statement 12.1.3 is about collecting and drying gases.” Why it fails Statement 12.1.3 is the six definitions — solvent, solute, solution, saturated solution, residue and filtrate. Gas collection and drying methods are not part of Topic 12 for this cycle. Correct Learn the six definitions for 12.1.3, in the official wording. Check If a revision resource lists upward delivery and drying agents under 12.1.3, it is describing an older specification.
• 23. “The final reading was \(28.60\ \mathrm{cm^3}\), so the titre is \(28.60\ \mathrm{cm^3}\).” Why it fails A reading is a position on a scale, not a volume delivered. Some liquid had already left the burette before the titration began. Correct Titre = final reading − initial reading. Write the subtraction even when the initial reading is \(0.00\ \mathrm{cm^3}\). Check Initial \(3.10\), final \(28.60\). Titre \(25.50\ \mathrm{cm^3}\), not \(28.60\).
• 24. “The end-point is when the solution turns pink.” Why it fails Which colour appears depends on the indicator chosen and on which solution is in the flask. There is no universal end-point colour. Correct The end-point is the first permanent colour change of the indicator — one that does not disappear on swirling. Name a colour only if the indicator was named. Check Adding acid to alkali containing phenolphthalein means watching pink disappear, not appear.
• 25. “Titres must agree within \(0.10\ \mathrm{cm^3}\).” Why it fails No such universal tolerance is stated in this syllabus. Quoting one as a rule asserts something you were not told. Correct Repeat until the careful titres agree closely, and use whatever tolerance the question or the instructions give you. Check Titres of \(23.10\), \(24.60\) and \(23.15\ \mathrm{cm^3}\): you can say the second is out of line with the other two without quoting any fixed number.
• 26. “You must spray the paper with ninhydrin.” Supplement 12.3.3 Why it fails The syllabus explicitly states that knowledge of a specific locating agent is not required. Naming one earns nothing and naming the wrong one can cost. Correct “Treat the dried paper with a locating agent, which makes the colourless spots visible so their positions can be measured.” Check When is a locating agent needed at all? Only when the separated substances are colourless.
• 27. “Use a separating funnel to separate the mixture.” Why it fails A separating funnel is not one of the five methods named in statement 12.4.1, so it is not the expected answer — and it only works at all for liquids that do not mix. Correct Choose from a suitable solvent, filtration, crystallisation, simple distillation and fractional distillation, and justify the choice from the property data. Check Ethanol and water are miscible, so no layers form; fractional distillation is the method.
• 28. “Chromium(III) gives a grey-green precipitate; copper(II) in excess ammonia gives a royal blue solution.” Why it fails Both are embellishments of the official wording. The notes say green and dark blue. Correct Chromium(III): green precipitate, soluble in excess. Copper(II) with excess ammonia: soluble, giving a dark blue solution. Check Iron(II) is also green — the same word, and the excess result is what separates them.
• 29. “Chlorine turns damp litmus red and then bleaches it.” Why it fails The required result is simply that chlorine bleaches damp litmus paper. Making the red stage compulsory risks writing an answer that does not match the result being marked. Correct “Bleaches damp litmus paper.” Check Ammonia's result is a colour change and chlorine's is bleaching — two different kinds of observation on the same kind of paper.
• 30. “Lithium is crimson, calcium is brick red, barium is apple green.” Why it fails None of those three words appears in the official flame-colour list, and a marker working from that list may not accept them. Correct Lithium red, sodium yellow, potassium lilac, calcium orange-red, barium light green, copper(II) blue-green. Check Which two pairs are easiest to confuse? The two reds and the two greens — and in each pair the qualifying word carries the whole distinction.

• The qualitative analysis notes are provided. The syllabus states that notes for use in qualitative analysis are supplied for both Paper 5 and Paper 6. That does not make 12.5 optional learning. Under timed conditions you have to read a result, match it to a row and combine it with a second result — and you will not do that fluently from a table you are meeting for the first time in the exam. Learn the rows so that the supplied notes become a check, not a lifeline. And note what the syllabus does not say: it names Paper 5 and Paper 6 only, so do not plan on having the notes in front of you on Papers 1 to 4.
• Decimal places carry meaning. A burette reading is recorded as \(22.35\ \mathrm{cm^3}\), not \(22.4\ \mathrm{cm^3}\), and an initial reading of exactly zero is recorded as \(0.00\ \mathrm{cm^3}\). Every reading in the same column of a table is written to the same number of decimal places, because the number of decimal places tells the reader what the instrument could resolve.
• On the rough run and on agreement. The first, quick titration overshoots on purpose — its job is to find roughly where the end-point lies so the later runs can be slowed down near it. Careful runs are then repeated until they agree closely, and it is those that are used. How close “closely” has to be is set by the question or the instructions you are working to; do not quote a fixed tolerance as though it were a universal rule, because none is stated in the syllabus.
• On locating agents. The syllabus asks you to describe the use of a locating agent when a mixture contains colourless substances — and states that knowledge of a specific locating agent is not required. So the creditworthy answer is about the job, not the name: “the paper is treated with a locating agent, which makes the colourless spots visible so their positions can be seen and measured”. Naming one is not wrong, but it earns nothing extra, and getting the name wrong can cost you.
• Two habits worth keeping. Write the equation in words before substituting, and finish with “no unit” when the answer is an \(R_f\). Both are quick, and both make your reasoning visible rather than leaving it to be inferred from a bare number. If a question gives distances in different units, convert first and say so in the working — a conversion done in your head is not part of your answer.
• The three-part answer. A full-credit 12.4.2 answer names the method, says which property difference makes it work, and states what you keep. “Fractional distillation” on its own is one third of an answer. “Fractional distillation, because the two liquids are miscible but have different boiling points, and the one boiling at \(65\ ^\circ\mathrm{C}\) is collected first” is all of it.
• What is reliable, and what is not. The dependable evidence for purity is the spread: pure substances change state at a fixed temperature, impure ones over a range. The direction in which an impurity shifts the value depends on the system, so build your answer on the range rather than asserting that an impurity always lowers a melting point or always raises a boiling point. If a question gives you both a known value and a measured range, use the range for purity and the position for identity, and say which you used for which.
• Two words that are worth marks on their own. Precipitate — not “it goes cloudy”, not “a solid”, and never “a blue solution” when a blue solid appeared. And excess — every cation test has two stages, and the second one is what separates aluminium from calcium and copper(II) from iron(II). If your answer to a cation test has only one observation in it, it is not finished.
• On chromium(III). The official result is “green precipitate, soluble in excess”. That is what to write. The notes do not specify a colour for the solution formed in excess, so do not invent one — and do not embellish the precipitate as “grey-green” or “dirty green” in a core answer. The word required is green, and the same word is used for iron(II).
• Two entries that are not ordinary precipitates. For ammonium, the official table has a dash: aqueous ammonia is not used to test for it, and inventing a result loses the mark. For calcium, the required result is “no precipitate or a very slight white precipitate”, and the qualification matters — write it in full, because “a white precipitate” would put calcium alongside aluminium, and “no reaction” on its own drops the alternative the notes allow for.
• Why the wording matters. The right-hand column is not a list of wrong observations — some of those words describe the flames rather well. It is a list of words that are not in the official notes, and a marker working from those notes may not accept them. There is no cost to writing the official word, and there is a real risk in writing anything else. This is one of the few places in chemistry where the exact vocabulary is the answer.
• What a full deduction answer contains. One line per test, in the order observation then inference; a sentence naming the cation and a sentence naming the anion, each pointing at its evidence; and only then the compound. If the evidence names an ion but not a formula — for example when the charge on the metal has not been established — name the ion and stop there. Inventing a formula the evidence does not support turns a correct deduction into a wrong answer.
• Control variables need a reason. Listing three things you kept the same earns little. Saying why each one had to be kept the same — because it would otherwise also affect the dependent variable — is what the mark is for. A quick test: if changing it would not change your measurement, it is not worth naming.
• Spotting an anomaly without guessing. Compare a result with the pattern the rest of the data makes, not with what you expected. Here, the means rise by about \(15\ \mathrm{cm^3}\) for each \(0.40\ \mathrm{mol/dm^3}\) step, so a value near \(60\ \mathrm{cm^3}\) is expected at \(1.60\) — which makes run 1's \(72\) the suspect, not run 2's \(58\). Naming which reading is anomalous, and saying what the pattern led you to expect, is worth more than the word “anomaly” on its own.

• Every candidate takes three papers, and which three depends on the route you are entered for. Both routes finish with the same practical choice: one paper from Paper 5 or Paper 6. Those two require the same experimental skills and the same experimental contexts and both test assessment objective AO3 — the difference is only whether you carry the experiments out yourself.
• Core route: Paper 1, Paper 3, and either Paper 5 or Paper 6. Questions are set on the Core subject content only. Eligible for grades C to G.
• Extended route: Paper 2, Paper 4, and either Paper 5 or Paper 6. Questions are set on the Core and Supplement content together — “Extended” means Core plus Supplement, never a separate syllabus. Eligible for grades A* to G.
• The practical paper is the same choice for both routes. Nothing in this chapter’s practical material is Extended-only.
• The qualitative analysis notes are provided. The syllabus states that notes for use in qualitative analysis are supplied for both Paper 5 and Paper 6. That does not make 12.5 optional learning. Under timed conditions you have to read a result, match it to a row and combine it with a second result — and you will not do that fluently from a table you are meeting for the first time in the exam. Learn the rows so that the supplied notes become a check, not a lifeline. And note what the syllabus does not say: it names Paper 5 and Paper 6 only, so do not plan on having the notes in front of you on Papers 1 to 4.
• Across the whole qualification the assessment objectives are weighted AO1 50%, AO2 30% and AO3 20%. Within components, the theory papers — Papers 1 to 4 — are 63% AO1 and 37% AO2, and the practical papers, Papers 5 and 6, are 100% AO3. So one fifth of your grade is earned by experimental skill and reasoning — the material in this chapter and the overlay at the end of it — and that fifth is the same on both routes.