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Titration Technique & Concordant Results

Titration (Paper 3): pipette/burette technique, meniscus reading, rough vs accurate titres, and concordant results (record to 2 d.p.).

  • SEC G3 Pure Chemistry 2027
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Learning objectives

  • name appropriate apparatus for the measurement of time, temperature, mass and volume; including burettes, pipettes, measuring cylinders and gas syringes
  • follow a sequence of instructions;
  • use techniques, apparatus and materials;
  • make and record observations, measurements and estimates;

Titration questions assess method and data handling, not just calculations. A careful sequence and a clear concordant-results table make your reasoning easy to follow.

1. Definition

Titration is a method for measuring the volume of one solution needed to reach the end-point with a known volume of another solution.

2. Key Ideas

  • Use a pipette for a fixed accurate volume (e.g., 25.0 cm³).
  • Use a burette to deliver a variable volume; 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).

3. Detailed Explanations

Quick Recall (details to check)
  • Read the bottom of the meniscus at eye level (avoid parallax error).
  • Titre = final burette reading − initial burette reading.
  • For a good end-point, obtain at least two titres within 0.20 cm³.

A. Apparatus and What Each One Does

ApparatusWhat it is used forTypical exam wording
pipettemeasure a fixed volume accurately“pipette 25.0 cm³”
burettedeliver a variable volume accurately“record initial and final readings”
conical flaskmixing (swirl safely)“add indicator”
white tilesee colour change clearly“place on white tile”

B. Steps of a High-Scoring Titration Method

  1. Rinse burette with the solution that will go in it, then fill and remove air bubbles.
  2. Use a pipette to transfer a fixed volume to a conical flask.
  3. Add a few drops of indicator.
  4. Add solution from the burette while swirling; near the end-point, add dropwise.
  5. Record initial and final burette readings to the nearest 0.05 cm³ (two decimal places) and calculate the titre.
  6. Repeat until you obtain concordant titres, then take the mean.

Mini-example (titre calculation): initial 0.00 cm³, final 24.40 cm³ → titre = 24.40 cm³.

Safety

Many acids and alkalis are corrosive/irritant. Wear eye protection and rinse spills with water.

C. 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.

Rule of thumb:

  • Use the mean of concordant titres.
  • Ignore the rough titre and any obvious anomaly.
Example Titres (Spot Concordant Results)Example titres showing a rough/anomalous result and three concordant results close together.Example Titres (Spot Concordant Results)Titre (cm³)Run
The axis is zoomed to show small differences. Ignore the rough/anomalous titre, then take the mean of concordant titres.
Data table
RunTitre
Rough24.80
T124.35
T224.40
T324.45

4. 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).

5. Exam Tips

Titration “method marks” checklist

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

6. Worked Examples

Modelled example 1

Identify Concordant Titres

Core

Problem

A student obtains titres of 24.80, 24.35, 24.40 and 24.45 cm³. Identify the concordant set.
Study the worked solution

  1. 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.

  2. Exclude the rough result

    Method

    Leave out 24.80 cm³.

    Reason

    It lies well outside the close cluster and is the rough/anomalous titre.

    Working

    Concordant titres: 24.35, 24.40 and 24.45 cm³.

Guided practice 2

Mean Titre

About 5 min

Problem

Calculate the mean titre from the concordant readings 24.35, 24.40 and 24.45 cm³.

Average only the selected concordant data

Sum of titres
Mean titre

Hints

Hint 1: denominator
There are three concordant titres, so divide their sum by three.
Hint 2: recording
Report the mean to the same two decimal places as the burette readings.
View solution step by step

  1. 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.

  2. 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

Find and correct the mistake

Learner technique

A learner views a burette from above, reads the top of the water meniscus and records one decimal place. Correct all three parts of the technique.

Correct viewing, meniscus and recording

Viewing position
Water meniscus point
Decimal places

View solution step by step

  1. 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.

  2. 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?

Minimal support

Procedure-purpose transfer

Explain how a first rough titration changes the way a learner should conduct later accurate titrations.

Connect approximate endpoint to later control

Rough run establishes
Near that volume later

Hints

Hint 1: information gained
The first run tells you approximately where the colour change occurs.
Hint 2: use it
In later runs, approach quickly at first, then slow down before reaching that volume.
View solution step by step

  1. 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.

  2. 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.

7. Mind Stretchers

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.

8. Quiz

Quiz time

Ready to check your understanding? Try the interactive quiz, then review any questions you missed.

Go to quiz