Titration and Volumetric Analysis
A titration finds an unknown concentration accurately. It carries a large number of marks — for the apparatus, the method, the readings and the calculation — and tutors gave more exam-technique advice here than for almost any other topic.
1. The apparatus
| Apparatus | Used for | Why |
|---|---|---|
| Burette | adding the solution gradually | measures variable volumes precisely (±0.05 cm³) |
| Pipette (with filler) | measuring a fixed volume (e.g. 25.0 cm³) | very accurate for one fixed volume |
| Conical flask | holding the measured solution | shape allows swirling without spills |
| White tile | placed under the flask | makes the colour change visible |
A pipette is not a measuring cylinder. Confusing them was recorded — a measuring cylinder is not accurate enough for a titration. Use a pipette for the fixed volume and a burette for the variable one.
Use a white tile or paper to see the endpoint clearly — tutors flagged this directly.
2. The method
- Rinse the burette with the solution it will contain, and the pipette with its solution
- Use the pipette to transfer a fixed volume (e.g. 25.0 cm³) into the conical flask
- Add 2–3 drops of indicator
- Fill the burette and record the initial reading
- Add from the burette, SWIRLING constantly, until the endpoint — a permanent colour change from one drop
- Record the final reading; titre = final − initial
- Repeat until you have concordant results
Swirling matters. Tutors flagged it specifically — without swirling, the solutions do not mix and the endpoint is missed.
Rinsing — a favourite exam question:
The burette and pipette must be rinsed with the solution they will hold, so residual water doesn’t dilute it. The conical flask must NOT be rinsed with the solution — rinse with distilled water only, since extra solution would add more moles.
Water left in the CONICAL FLASK does not affect the result, because it doesn’t change the number of moles present. A recorded error claimed the opposite. Water in the burette or pipette does matter, because it dilutes the solution being measured.
3. Choosing an indicator
Use an indicator with a SHARP colour change at the endpoint.
| Titration | Suitable indicator |
|---|---|
| Strong acid + strong alkali | methyl orange or phenolphthalein |
| Strong acid + weak alkali | methyl orange |
| Weak acid + strong alkali | phenolphthalein |
Never use universal indicator in a titration — tutors flagged this directly. It changes through a range of colours rather than sharply, so the endpoint cannot be pinpointed.
Uncertainty about the choice of indicator was recorded — and note that only 2–3 drops are needed. Too much indicator affects the result.
For preparing a pure salt: repeat the titration without indicator, using the titre you found — so the product isn’t contaminated by the dye. Tutors flagged this as an exam point.
4. Reading the burette
Read to the BOTTOM OF THE MENISCUS, at eye level, to 2 decimal places ending in .00 or .05.
Example: 24.35 cm³, not 24.4.
Misreading burette readings was a recorded error, as was an incorrect initial reading. Take your time, and remember the burette scale runs downwards — zero is at the top.
Concordant titres:
Results are concordant when they agree within 0.10 cm³.
Average only the CONCORDANT titres — discard the rough (first) titration and any anomalies.
Subtract carefully: titre = final − initial. Incorrect subtraction leading to a wrong volume was recorded.
5. The calculation
1. Write the BALANCED equation — you need the mole ratio. 2. Find the MOLES of the substance you know everything about (n = c × V, with V in dm³). 3. Use the MOLE RATIO to find the moles of the unknown. 4. Calculate the CONCENTRATION (c = n ÷ V).
Worked example. 25.0 cm³ of NaOH needs 22.5 cm³ of 0.100 mol/dm³ HCl.
HCl + NaOH → NaCl + H₂O (ratio 1 : 1)
- Moles HCl = 0.100 × (22.5 ÷ 1000) = 0.00225 mol
- Ratio 1:1, so moles NaOH = 0.00225 mol
- c(NaOH) = 0.00225 ÷ (25.0 ÷ 1000) = 0.00225 ÷ 0.025 = 0.09 mol/dm³
Convert cm³ to dm³ by dividing by 1000 — the commonest error in the calculation.
Use the mole ratio from the balanced equation. For H₂SO₄ + 2NaOH the ratio is 1 : 2, not 1 : 1. Misunderstanding the stoichiometric ratio in a titration calculation was recorded.
To find concentration in g/dm³: multiply the mol/dm³ answer by the Mr.
6. Neutralisation equations
acid + alkali → salt + water
Water is the only other product — there is no oxygen. A recorded error included oxygen among the products.
The ionic equation for any strong acid–alkali neutralisation:
H⁺(aq) + OH⁻(aq) → H₂O(l)
Include state symbols in ionic equations — tutors flagged this.
Sodium hydroxide and potassium hydroxide are different alkalis — confusing them was recorded. Check which the question names, because the Mr differs (40 vs 56).
7. Sources of error and improvements
Errors:
- Misreading the burette, or parallax
- Overshooting the endpoint
- Using too much indicator
- Air bubble in the burette tip
- Not swirling
Improvements:
- Add dropwise near the endpoint
- Repeat for concordant results
- Use a white tile
- Ensure the burette tip is filled with no air bubble
Give more than one source of error when asked — a recorded error identified only one where several were available.
Be specific. Name the actual mechanism, not “human error”.
8. Mistakes that cost marks
Using a measuring cylinder instead of a pipette.
Using universal indicator.
Rinsing the conical flask with the solution.
Saying water in the conical flask affects the result.
Reading the burette to 1 decimal place, or from the top of the meniscus.
Averaging non-concordant titres.
Not converting cm³ to dm³.
Using a 1:1 ratio when the equation says otherwise.
Including oxygen in neutralisation products.
Omitting state symbols from ionic equations.
Frequently asked questions
What apparatus measures the fixed volume? A pipette — accurate for one volume.
What does the burette do? Adds the second solution gradually, measuring a variable volume precisely.
Why not use universal indicator? It changes over a range, giving no sharp endpoint.
Should I rinse the conical flask with the solution? No — distilled water only. Extra solution would add moles.
Does water in the conical flask matter? No — it doesn’t change the number of moles.
How do I read a burette? Bottom of the meniscus, at eye level, to 2 d.p.
What are concordant titres? Results agreeing within 0.10 cm³ — average only these.
What’s the first step in the calculation? Write the balanced equation for the mole ratio.
How do I convert cm³ to dm³? Divide by 1000.
What is the ionic equation for neutralisation? H⁺(aq) + OH⁻(aq) → H₂O(l).
Quick revision checklist
- I know the apparatus and why each is used
- I can give the method in order, including swirling
- I know what to rinse with what, and why
- I know water in the conical flask is harmless
- I can choose a suitable indicator and know to use 2–3 drops
- I never use universal indicator
- I read the burette to 2 d.p. at the bottom of the meniscus
- I average only concordant titres
- I can do the full calculation, converting to dm³
- I use the mole ratio from the balanced equation
- I know the neutralisation equation and its ionic form
- I can give several specific sources of error
These notes cover titration and volumetric analysis in the Cambridge IGCSE Chemistry (0620) syllabus and are written for Grade 9–11 / Year 10–11 students. They are based on teaching patterns observed across a large set of one-to-one IGCSE Chemistry lessons, with particular attention to the errors students make most often and the wording examiners reward. Always check the current syllabus for your own exam series.
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