Overview
What you’ll learn
- Calculate concentrations in g/dm³ and the mass needed for any solution.
- Describe the full titration method — burette, pipette, indicator, endpoint — and why concordant repeats matter.
- Convert between g/dm³ and mol/dm³ using the Mr (Chemistry only, Higher).
- Work a complete titration calculation through moles and the equation ratio (Chemistry only, Higher).
Specification checklist (AQA 8462 · Edexcel 1CH0 · OCR Gateway J248)
Statements are paraphrased from the shared DfE subject content and grouped by tier. Foundation content is studied by every student; Higher statements are examined on Higher-tier papers only, and statements badged Chemistry only are examined in separate (triple) Chemistry, not Combined Science. QuizQuip is not affiliated with AQA, Pearson Edexcel or OCR.
Higher — Higher tier only
- 8.1Calculate the concentration of a solution in g/dm³ from the mass of solute and the volume of solution, converting cm³ to dm³ by dividing by 1000.
- 8.2Calculate the mass of solute needed to make a solution of a given concentration and volume.
- 8.3Describe the titration technique: rinse and fill a burette with acid, measure 25.0 cm³ of alkali with a pipette into a conical flask, add a few drops of indicator, and run the acid in until the colour just changes at the endpoint.Chemistry only
- 8.4Explain the practical refinements: a rough run first, then repeats with the acid added dropwise near the endpoint, keeping only concordant titres (within 0.1 cm³) to calculate the mean.Chemistry only
- 8.5Calculate the concentration of a solution in mol/dm³ (moles of solute ÷ volume in dm³) and convert between mol/dm³ and g/dm³ via the Mr.Chemistry only
- 8.6Carry out titration calculations: use moles = concentration × volume to find the moles reacting, apply the equation ratio, and work back to the unknown concentration.Chemistry only
- 8.7Explain why titrations are used to make salts from soluble reactants (such as ammonium chloride) where no excess insoluble solid can be filtered off, and why no indicator is used when preparing a salt this way.Chemistry only
- 8.8Describe the uncertainty of a burette reading (±0.05 cm³) and how repeating titrations and averaging concordant values reduces the uncertainty of the result.Chemistry only
Key points
- 1Concentration = mass ÷ volume; 1 dm³ = 1000 cm³, so 25 cm³ = 0.025 dm³.
- 2A g/dm³ answer is just grams per litre of solution.
- 3Titration kit: burette (acid, reads to 0.1 cm³), pipette (exactly 25.0 cm³ of alkali), conical flask, 2–3 drops of indicator.
- 4Run a rough titration first, then repeat dropwise near the endpoint; keep concordant titres within 0.10 cm³ and average them.
- 5(Chemistry only, Higher) concentration in mol/dm³ = moles ÷ dm³; convert to g/dm³ by multiplying by the Mr.
- 6(Chemistry only, Higher) Titration calculation road: moles = conc × vol → equation ratio → unknown moles → concentration.
- 7Titration-made salts (e.g. ammonium chloride) are crystallised without indicator — pure solution, no contamination.
Notes · 1 of 5
Concentration in g/dm³
Mass per litre: divide the grams by the volume in dm³.
Concentration says how much solute is dissolved in a given volume of solution. In g/dm³ it is simply mass ÷ volume — but only once the volume is in dm³. Since 1 dm³ = 1000 cm³, a 250 cm³ flask is 0.25 dm³. Dissolve 11.7 g of sodium chloride in water and make up to 500 cm³: the concentration is 11.7 ÷ 0.5 = 23.4 g/dm³. The reverse works too: to make 250 cm³ of 40 g/dm³ sugar solution you need 40 × 0.25 = 10 g of sugar.
Notes · 2 of 5
The titration technique (Chemistry only)
A pipette delivers exact volume; a burette measures what reacts with it — to the drop.
- 11. Rinse and fill
Rinse the burette with the acid, then fill it and record the initial reading to 0.1 cm³ (e.g. 0.50 cm³). Rinse the pipette with alkali, then draw up exactly 25.0 cm³ and release it into a conical flask.
- 22. Indicator
Add 2–3 drops of indicator (e.g. methyl orange or phenolphthalein) — no more, or it affects the result.
- 33. Rough run
Open the tap and let acid run in quickly, swirling, until the colour just changes. Read the burette — this rough titre tells you roughly where the endpoint lies.
- 44. Accurate runs
Repeat, but approach the endpoint drop by drop, swirling constantly, and rinse the flask walls with distilled water. Record the final reading; titre = final − initial.
- 55. Concordance and mean
Repeat until two titres agree within 0.10 cm³ — concordant. Discard the rough value, average the concordant ones.
| Run | Final / cm³ | Initial / cm³ | Titre / cm³ | Used for mean? |
|---|---|---|---|---|
| Rough | 22.10 | 0.00 | 22.10 | No |
| 1 | 22.20 | 0.00 | 22.20 | Yes |
| 2 | 44.30 | 22.20 | 22.10 | Yes |
| 3 | 66.60 | 44.30 | 22.30 | No (not concordant) |
The mean uses runs 1 and 2: (22.20 + 22.10) ÷ 2 = 22.15 cm³. Run 3 at 22.30 sits 0.20 cm³ from 22.10 — outside 0.1 — so it is excluded. A burette reads to 0.1 cm³, so each reading carries ±0.05 cm³ uncertainty; concordant repeats shrink the uncertainty of the final answer.
Notes · 3 of 5
Concentration in mol/dm³ (Chemistry only, Higher)
Divide the moles of solute by the volume — and convert to g/dm³ via the Mr.
Chemists usually quote concentrations in moles per dm³: concentration (mol/dm³) = moles of solute ÷ volume (dm³). A 1 mol/dm³ acid holds 1 mole of acid per litre. The two units connect through the Mr: g/dm³ = mol/dm³ × Mr. So 0.5 mol/dm³ sulfuric acid (Mr 98) is 0.5 × 98 = 49 g/dm³; and a 20 g/dm³ NaOH solution (Mr 40) is 20 ÷ 40 = 0.5 mol/dm³.
Notes · 4 of 5
Titration calculations (Chemistry only, Higher)
Conc × vol → moles; ratio; moles → conc. One road, four stations.
Notes · 5 of 5
Making salts by titration (Chemistry only)
When both reactants are soluble, there is nothing to filter — so measure exactly instead.
The Chapter 7 method needs an insoluble base to remove in excess. When both reactant and salt are soluble — ammonium chloride from ammonia solution and hydrochloric acid — titration replaces the excess-and-filter trick. Titrate to find the exact reacting volumes once (with indicator), then repeat the reaction using exactly those volumes without any indicator, so the solution is pure ammonium chloride in pure water. Evaporate to crystallisation point and cool; pure crystals grow. No filtration is needed because nothing insoluble was ever added.
Revise
Key terms
The words examiners expect you to use precisely.
- Concentration
- The amount of solute dissolved per volume of solution, in g/dm³ or (Chemistry only) mol/dm³.
- dm³
- One litre: 1000 cm³. Volumes must be in dm³ for concentration calculations.
- Solute
- The solid dissolved in a solvent to make a solution.
- Burette
- A long graduated tube with a tap, reading to 0.1 cm³, used to run acid into the flask during a titration.
- Pipette
- A glass tube that delivers one fixed, precise volume — usually 25.0 cm³.
- Endpoint
- The point where the indicator just changes colour, showing neutralisation is complete.
Show 6 more key termsShow fewer key terms
- Titre
- The volume of acid run in during a titration: final burette reading minus initial.
- Concordant titres
- Repeat titres agreeing within 0.10 cm³, the only ones averaged for the result.
- mol/dm³
- Moles of solute per dm³ of solution (Chemistry only, Higher); g/dm³ ÷ Mr.
- Rough titration
- A quick first run to locate the endpoint approximately before accurate repeats.
- Indicator
- A dye that changes colour sharply at the endpoint; 2–3 drops only.
- Standard solution
- A solution of accurately known concentration.
Revise
Common mistakes
Where students most often lose marks in this chapter — and what to do instead.
Mistake: Dividing grams by the volume in cm³.
Concentration units need dm³ — 250 cm³ is 0.25 dm³, not 250.
Instead: Convert the volume first: ÷ 1000.
Mistake: Averaging all titres including the rough run.
The rough run overshot by design.
Instead: Discard the rough, average only concordant titres (within 0.10 cm³).
Show 10 more mistakesShow fewer mistakes
Mistake: Forgetting to subtract the initial burette reading.
The titre is the difference, final − initial.
Instead: 22.10 − 0.50 = 21.60 cm³.
Mistake: Using the equation ratio 1 : 1 for sulfuric acid + sodium hydroxide.
H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O is 1 : 2.
Instead: Always write and balance the equation before riding the ratio.
Mistake: Converting mol/dm³ to g/dm³ by dividing by the Mr.
That divides grams away.
Instead: g/dm³ = mol/dm³ × Mr; mol/dm³ = g/dm³ ÷ Mr.
Mistake: Adding lots of indicator “to see the colour better”.
Indicators are themselves acids or bases; extra drops shift the result.
Instead: 2–3 drops only.
Mistake: Rinsing the conical flask with alkali before the titration.
Leftover alkali adds extra moles that the pipette never measured.
Instead: Rinse the flask with distilled water only — water adds volume, not moles, so it cannot change the result.
Mistake: Rinsing the burette with distilled water after cleaning, then filling with acid.
Water dilutes the acid, changing its true concentration.
Instead: Rinse the burette with the acid it will hold.
Mistake: Reading the burette from the top of the meniscus.
Burettes are calibrated to the bottom of the meniscus.
Instead: Read the bottom of the meniscus at eye level.
Mistake: Saying one titration is enough if done carefully.
A single reading carries the full burette uncertainty and any misjudged endpoint.
Instead: Repeat until concordant and average — that is the entire point of the repeats.
Mistake: Writing the titration concentration answer in g/dm³ when mol/dm³ was asked.
The units are different quantities linked by the Mr.
Instead: Check the unit asked and convert: × Mr for g/dm³, ÷ Mr for mol/dm³.
Mistake: Using an indicator when preparing a salt by titration.
The indicator dye would contaminate the salt solution.
Instead: Titrate once with indicator to find the volumes, then repeat cleanly without it.
Check yourself
Quick quiz
30 questions with instant explanations. About 5 minutes.
Question 1 of 3
- Question 1: current question
- Question 2: not answered
- Question 3: not answered
Calculate g/dm³
A solution contains 20 g of solute in 500 cm³. Its concentration is
Ready for more practice on Titration?
Generate a fresh 5-question adaptive drill grounded in this chapter’s GCSE key points. Free with your study account.
Practise
Topical questions
18 exam-style questions with model answers and mark schemes.
A set of structured and calculation questions matched to this chapter, in three tiers, each with a model answer, mark scheme and examiner tip. Higher-tier and Chemistry-only questions are tagged.
Practise topical questionsExam practice
Practice paper
A 30-mark paper in the style of a GCSE paper, with a separate mark scheme. Give yourself 40 min.
Question paper
Chapter 8 Practice Paper
30 marks · 40 min · 6 pages
10 multiple-choice questions and structured questions with answer lines. Chapter 8: concentration in g/dm³, the titration practical and concordant titres, mol/dm³ and titration calculations (Chemistry-only, Higher, badged).
Mark scheme
PROChapter 8 Practice Paper — mark scheme
Answers · Marking points · 2 pages
Model answers with a mark for each creditworthy point — for marking at home or in class.
How is this chapter examined?
Paper 1
1 h 45 · 100 marks
Chapters 1–11: atoms, bonding, quantitative, chemical and energy changes
Paper 2
1 h 45 · 100 marks
Chapters 12–18: rates, organic, analysis, atmosphere, resources
Tiers
Foundation (grades 1–5) · Higher (grades 4–9)
Higher assumes all Foundation content; a periodic table is printed
Want a full paper? Try the Paper 1-style (Foundation), Paper 1-style (Higher), Paper 2-style (Foundation), Paper 2-style (Higher), Required practicals practice sets.
Questions
Frequently asked questions
Is titration content Higher only?
In separate GCSE Chemistry, everything in this chapter is Higher-tier: the DfE subject content underlines the whole amount-of-substance section, including concentration in g/dm³. (g/dm³ on its own also appears in Combined Science, but mol/dm³, titration calculations and the titration required practical are separate-Chemistry only.)
Which indicator should I name?
For strong acid + strong alkali, methyl orange or phenolphthalein both work. Name one, use 2–3 drops, and describe the colour change direction (e.g. phenolphthalein pink → colourless as acid is added to alkali).
Why 0.10 cm³ for concordance?
It matches the burette resolution: two readings each ±0.05 cm³ can legitimately differ by 0.1 cm³. Anything beyond that is a real technique difference, not instrument noise.
What is the single most common calculation error?
Forgetting to convert cm³ to dm³. Write the conversion explicitly (÷1000) every single time and you will never lose those marks.
Does QuizQuip have any connection to the exam boards?
No. AQA, Pearson Edexcel and OCR are named only to identify the specifications this content supports. QuizQuip is not affiliated with, endorsed by, or connected to AQA, Pearson Edexcel or OCR, and no past-paper or specimen material is reproduced.
How does this connect to the salt-making practical from Chapter 7?
They are alternative routes to the same product. Use excess insoluble base when you can filter; use titration when everything is soluble. Both end the same way: evaporate to crystallisation, cool, dry.
Up next
Chapter 9: Reactivity series and metal extraction