Titration technique and concordant results
Titration (Paper 3): pipette/burette technique, meniscus reading, rough vs accurate titres, and concordant results (record to 2 d.p.).
On this page
A titration measures how much of one solution reacts with a measured portion of another. Accurate transfers, a repeatable end-point and clearly recorded readings make the result useful for later concentration calculations.
What the skill involves
Titration is a method for measuring the volume of one solution needed to reach the end-point with a known volume of another solution.
What you need to know
- Use a pipette for a fixed accurate volume (e.g., 25.0 cm³).
- Use a burette to deliver a variable volume. For a standard burette graduated in 0.1 cm³, normally read to the nearest 0.05 cm³ and record two decimal places.
- Do a rough titration first, then repeat to get concordant titres.
- A titre is the volume delivered from the burette (final reading − initial reading).
Putting the skill into practice
- Read the bottom of a clear, concave meniscus at eye level.
- Titre = final burette reading − initial burette reading.
- Check that your accurate titres agree before calculating a mean; follow any tolerance stated in the instructions.
Apparatus and what each one does
| Apparatus | What it is used for | Typical exam wording |
|---|---|---|
| pipette | measure a fixed volume accurately | “pipette 25.0 cm³” |
| burette | deliver a variable volume accurately | “record initial and final readings” |
| conical flask | mixing (swirl safely) | “add indicator” |
| white tile | see colour change clearly | “place on white tile” |
Carrying out a titration
- Rinse the clean burette with the solution that will go in it. Fill it, run solution through the tap to fill the tip and remove air bubbles, and remove the filling funnel.
- Rinse a clean volumetric pipette with the solution to be transferred. Use a pipette filler to draw liquid above the mark, then adjust the meniscus to the mark at eye level. Transfer the fixed volume to a conical flask rinsed with distilled water. Let a standard transfer pipette drain under gravity; do not blow out the small amount left in its tip.
- Add a few drops of the instructed indicator and place the flask on a white tile. Record the initial burette reading at eye level; it need not be zero.
- Do a rough titration to locate the approximate end-point. In later accurate runs, swirl throughout and add solution dropwise near that volume. Wash splashes on the flask walls down with a little distilled water so they react too.
- Stop at the instructed end-point colour that persists after swirling. Record the final burette reading using the same convention as the initial reading, then calculate the titre.
- Repeat accurate titrations until the titres agree within the stated tolerance. Calculate the mean of the selected concordant accurate titres, keeping all original readings in the table.
Why use different rinsing liquids?
| Apparatus | Final rinse | Reason |
|---|---|---|
| Burette | Solution it will deliver | Remaining water would dilute that solution. |
| Pipette | Solution it will transfer | Remaining water would dilute the measured portion. |
| Conical flask | Distilled water | Water adds no extra reacting solute. Rinsing with the reactant solution would leave an unmeasured amount in the flask. |
Mini-example (titre calculation): initial 0.00 cm³, final 24.40 cm³ → titre = 24.40 cm³.
Wear eye protection, use a pipette filler and follow the handling instructions for the supplied acid, alkali and indicator. Tell your teacher about spills and follow the instructed clean-up procedure.
Concordant results (what they mean)
Concordant titres are titres that closely agree. For the K324 practical guidance, obtain at least two titres within 0.20 cm³ when the end-point is good.
Choosing the readings to average:
- Use the mean of concordant titres.
- Exclude the rough titre from the final mean because its purpose was to locate the end-point.
- If accurate titres disagree, investigate possible overshoot, air bubbles or leaks and repeat. Retain the readings and explain your choice of concordant set; do not delete results merely to make the mean look better.
Data table
| Run | Titre |
|---|---|
| Rough | 24.80 |
| T1 | 24.35 |
| T2 | 24.40 |
| T3 | 24.45 |
Practise below: do a rough titration, then add the acid drop by drop near the end-point until two titres agree, reading the burette at eye level each time.
Titration 1. 25.0 cm³ of sodium hydroxide sample A with methyl orange is in the flask. The burette of 0.100 mol/dm³ hydrochloric acid reads about 0.20 cm³. The solution is yellow.
- Volume added
- 0.00 cm³
- pH
- 12.93
- [H⁺]
- 1.2 × 10⁻¹³ mol/dm³
- Titration
- 1 (rough)
Try this
0 of 4 doneWith universal indicator, add alkali to hydrochloric acid until the solution turns violet. (not done yet)
The colour runs from red through green to violet as OH⁻ ions remove H⁺ ions (H⁺ + OH⁻ → H₂O). Near neutralisation one drop takes the pH from about 4 to 10.
Titrate ethanoic acid with sodium hydroxide to the end point twice: once with methyl orange and once with phenolphthalein. (not done yet)
The steep part runs from about pH 7.5 to 10, so phenolphthalein or thymolphthalein changes within a drop of equivalence. Methyl orange changes in the buffer region, far too early.
Titrate ethanoic acid with sodium hydroxide past equivalence, then drag the graph cursor to the half-equivalence point. (not done yet)
Half the CH₃COOH has become CH₃COO⁻, so the two concentrations are equal and pH = pKₐ = 4.76. Around this point the curve is flattest: the buffer region.
Find the concentration of a sodium hydroxide sample: do a rough titration, then accurate ones until two titres agree within 0.20 cm³. (not done yet)
Average the concordant titres. Moles of HCl = concentration × titre; the 1 : 1 ratio gives the moles of NaOH in 25.0 cm³, so divide by 0.0250 dm³.
Your readings
| # | Final reading / cm³ | Initial reading / cm³ | Titre / cm³ | Remove |
|---|---|---|---|---|
| No readings yet. Set up a measurement, then record it. | ||||
Avoiding common mistakes
- Not recording readings to the nearest 0.05 cm³ with the final digit 0 or 5.
- Not removing the funnel from the burette during titration.
- Adding too fast near the end-point (overshooting).
- Averaging titres that are not concordant.
- Forgetting to swirl the flask (poor mixing).
Explaining your method
pipette fixed volume → indicator in flask → burette readings (nearest 0.05 cm³) → swirl → add dropwise near end-point → repeat to concordant → mean of concordant titres
Worked examples
Modelled example 1
Identify Concordant Titres
Problem
Study the worked solution
Compare the close cluster
Method
Group 24.35, 24.40 and 24.45 cm³.Reason
The greatest difference within this set is 0.10 cm³, which is within the 0.20 cm³ practical guidance.Working
Range: 24.45-24.35 = 0.10 cm³.Exclude the rough result
Method
Leave out 24.80 cm³.Reason
It is the labelled rough run, used to locate the end-point rather than obtain an accurate titre.Working
Concordant titres: 24.35, 24.40 and 24.45 cm³.
Guided practice 2
Mean Titre
Problem
Average only the selected concordant data
Hints
Hint 1: denominator
Hint 2: recording
View solution step by step
Add the concordant titres
Method
Sum only 24.35, 24.40 and 24.45.Reason
The rough or anomalous reading is not part of the selected concordant set.Working
24.35 + 24.40 + 24.45 = 73.20 cm³.Calculate and record the mean
Method
Divide by three and retain two decimal places.Reason
There are three readings, all recorded with burette precision.Working
73.20/3 = 24.40 cm³.
Common misconception 3
Reading the Burette
Learner technique
Correct viewing, meniscus and recording
View solution step by step
Correct viewing and meniscus
Method
View at eye level and read the bottom of the concave meniscus.Reason
Eye level avoids apparent scale displacement, and the lower curve is the standard aqueous reference point.Working
Eye level; bottom of meniscus.Correct the record
Method
Write the reading to two decimal places.Reason
This communicates the precision supported by the burette scale.Working
Technique: bottom at eye level; record 2 d.p.
Challenge 4
Why Do a Rough Titration?
Procedure-purpose transfer
Connect approximate endpoint to later control
Hints
Hint 1: information gained
Hint 2: use it
View solution step by step
Use the rough run as a locator
Method
Find an approximate endpoint volume.Reason
The first run is exploratory, so it narrows the interval where the indicator will change.Working
Rough titre estimates the endpoint.Adapt later titrations
Method
Approach that volume carefully and add titrant dropwise while swirling.Reason
Slower addition near the endpoint reduces overshoot and helps produce accurate concordant titres.Working
Use the rough value to know when to slow down; do not include it in the concordant mean.
Try it independently
Mind stretcher 1: Funnel Left in the BuretteExtension
Question: A student leaves a funnel in the burette during titration. Explain why this can make the titre wrong.
Show Answer
Answer: Drops can fall from the funnel into the burette during the titration, increasing the volume delivered without being recorded. This makes the titre unreliable.
Mind stretcher 2: Non-Concordant MeanExtension
Question: A student averages 23.90 and 24.60 cm³ to get 24.25 cm³. Why is this poor practice?
Show Answer
Answer: The titres are not concordant (difference is too large), so the mean is not reliable. The student should repeat the titration until concordant titres are obtained.
Practise and check
See what you know across this topic, then go back to anything you got wrong.
Syllabus and review details
- SEC G3 Pure Chemistry 2027 · 2027
Content structure and subject content, PDF pages 9–24
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