New
New
Year 10
OCR
Higher

Titrations: analytical technique

I can accurately measure the volume of an acid of an unknown concentration that neutralises an alkali of a known concentration.

New
New
Year 10
OCR
Higher

Titrations: analytical technique

I can accurately measure the volume of an acid of an unknown concentration that neutralises an alkali of a known concentration.

Lesson details

Key learning points

  1. In a titration, a trial investigation helps estimate the amount of acid needed to neutralise the alkali.
  2. Near the end point, add the acid drop by drop whilst swirling the solution in the conical flask to mix.
  3. Placing a white tile under the conical flask enhances the visibility of the colour change and accuracy of readings.
  4. Volume readings should be taken at eye level from the bottom of the meniscus.
  5. Concordant titres are typically within ±0.10 cm³.

Common misconception

Pupils often believe that any small colour change signals the end point, leading to inaccurate titrations.

Emphasise the importance of adding the titrant drop by drop near the end point and ensure pupils understand that the end point is reached only when the colour change is persistent.

Keywords

  • Titrant - the solution of known concentration added from the burette in titration

  • Analyte - the solution of unknown concentration in the conical flask in titration

  • Concentration - the amount of a solute dissolved in a certain volume of solvent

  • Concordant - readings within a certain range; for titrations, these usually need to be within ±0.10 cm³ of each other

  • Titre - the volume of titrant needed to reach the end point in a titration

Encourage pupils to practice taking precise readings at eye level with the burette and stress the importance of achieving concordant titres for reliable results.
Teacher tip

Equipment

burettes, volumetric pipettes/measuring cylinders, mini funnels, conical flasks, 0.1 M solution of HCl and an 'unknown conc' of NaOH, white tiles, pipette fillers, phenolphthalein indicator

Content guidance

  • Risk assessment required - chemicals
  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
What is titration used for in chemistry?
Correct answer: To completely neutralise an acid with an alkali.
To mix acids and alkalis randomly.
To measure the pH of a solution.
To heat up acids and alkalis.
Q2.
Match the following terms from titrations to their correct definitions.
Correct Answer:titration,A technique to find volumes of reacting solutions.

A technique to find volumes of reacting solutions.

Correct Answer:volume,The space matter occupies, often in cm³.

The space matter occupies, often in cm³.

Correct Answer:end point,When enough solution is added for a complete reaction.

When enough solution is added for a complete reaction.

Correct Answer:strong acid,An acid that fully ionises in water.

An acid that fully ionises in water.

Q3.
What is the curve on the surface of a liquid in a container called?
Correct Answer: meniscus, Meniscus
Q4.
How do you know the end point of a titration has been reached?
Correct answer: The indicator changes colour and stays that colour.
The solution becomes cloudy.
The indicator changes colour briefly, then fades.
The volume of acid stops changing.
Q5.
Which of the following statements about strong acids in water is correct?
They do not ionise at all.
They partially ionise.
Correct answer: They ionise completely.
Q6.
Which of the following indicators are suitable to use in a titration?
universal indicator
litmus paper
Correct answer: phenolphthalein
Correct answer: methyl orange

6 Questions

Q1.
Match the following key terms to its definition.
Correct Answer:titrant,Solution of known concentration in the burette.

Solution of known concentration in the burette.

Correct Answer:analyte,Solution of unknown concentration in the conical flask.

Solution of unknown concentration in the conical flask.

Correct Answer:concentration,Amount of solute dissolved in a solvent.

Amount of solute dissolved in a solvent.

Correct Answer:concordant,Titres within ±0.10 cm³ of each other.

Titres within ±0.10 cm³ of each other.

Correct Answer:titre,Volume of titrant needed to reach the end point.

Volume of titrant needed to reach the end point.

Q2.
Why is it important to perform a trial titration first?
To heat up the solution.
Correct answer: To estimate how much acid to add.
To get a colour change faster.
To neutralise the alkali quickly.
Q3.
Why is acid added drop by drop near the end point in titration?
To speed up the reaction.
To make the solution more concentrated.
To reduce splashing.
Correct answer: To ensure accuracy.
Q4.
Sort the steps of a titration into the correct order, starting with performing a trial titration.
1 - Perform a trial titration to estimate the amount of titrant needed.
2 - Fill the burette with the titrant (acid).
3 - Add the analyte (alkali) to the conical flask.
4 - Add indicator to the analyte in the flask.
5 - Begin adding titrant quickly from the burette.
6 - Slow down and add drop by drop near the end point.
7 - Stop when the indicator changes colour and stays that colour.
Q5.
At what point should you take the volume reading from a burette?
Centre of the solution.
Correct answer: Bottom of the meniscus.
Top of the liquid.
From the edge of the meniscus.
Q6.
What does it mean if titres are concordant?
They differ by more than 0.10 cm³.
Correct answer: They differ by less than 0.10 cm³.
They are exactly the same.

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