Titrations

This lesson covers:

  1. What a titration is
  2. The equipment used in a titration 
  3. The steps in carrying out a titration
  4. The indicators used in titrations

What is a titration?


A titration is an experimental technique used to find an unknown concentration of an acid or an alkali.

Titration equipment

Diagram showing titration equipment including a pipette, burette, conical flask, and white tile.


  1. A pipette to accurately measure a certain volume of acid or alkali (normally 25 cm3)
  2. A conical flask to contain the liquid from the pipette
  3. A burette to add alkali or acid to the the conical flask
  4. A white tile to place the conical flask on

Method


The following steps outline how you'd perform a titration in which an acid is added to an alkali:

Illustration showing a pipette dispensing acid into an alkali solution with a label of 25 cm3.

1Use the pipette to add 25 cm3 of alkali to a clean conical flask.

Diagram showing an indicator being added to an alkali solution in a conical flask.

2Add a few drops of indicator and put the conical flask on a white tile.

Diagram showing the titration process with acid being added to alkali and noting the volume.

3Fill the burette with acid and note the starting volume.

Illustration showing a titration setup with acid being added to alkali.

4Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.

Illustration showing the endpoint of a titration where the acid has neutralised the alkali and the indicator changes colour.

5Stop adding the acid when the end-point is reached (this is when the acid has neutralised the alkali and the indicator changes colour).

Diagram showing how to calculate the volume of acid added during titration by noting the final volume.

6Note the final volume reading, and calculate how much acid you added in total.

Illustration showing the repetition of titration method with three setups of burettes and conical flasks.

7Repeat the titration until you get 'concordant results', which means volumes of acid that are within 0.10 cm3 of each other.

8Use the concordant results to calculate the mean volume of acid required to neutralise the alkali.

Indicators


When doing a titration, you must place an indicator in the conical flask so that you can tell when the acid has neutralised the alkali. Indicators show this by changing colour as the pH changes from acidic to alkaline.

Illustration showing a conical flask being swirled to evenly distribute the acid during a titration.

It is important to swirl the conical flask as you add the acid from the burette in order to evenly distribute it, and ensure that the colour change occurs as soon as neutralisation takes place.


It's also important that you place the conical flask on a white tile, so you can more easily see when the colour change takes place.

Diagram showing the colour change of indicators in a titration with acid and alkali in the flask.

So far in our examples we have talked about adding acid from the burette to an alkali in the flask, but be aware titrations can also be done the other way around, with the acid in the flask, and the alkali in the burette.


Because you always add the indicator to the flask (and not the burette), you may need to use a different indicator, depending on whether it's an alkali or acid in the flask.

There are 3 different type of indicators (and their respective colour changes) you should know:

Illustration showing litmus indicator colour change in alkaline and acidic solutions.

Litmus is red in acidic solutions and blue in alkaline solutions

Illustration showing phenolphthalein indicator changing colour from pink in alkaline to colourless in acidic solution.

Phenolphthalein is colourless in acidic solutions and pink in alkaline solutions

Illustration showing methyl orange indicator colour change in alkaline and acidic solutions.

Methyl orange in red in acidic solutions and yellow in alkaline solutions 

Illustration of a pipette with a pink bulb used in titration experiments.

What piece of apparatus is shown in the image above?

Pipette

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Which precaution reduces the risk of harm from acid burns?

Tying back long hair

Wearing gloves 

Working in a fume cupboard

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Illustration showing the swirling of a conical flask during titration.

Why should you swirl the conical flask during the titration?

To reduce spilling

To speed up the titration

To evenly distribute the added acid/alkali

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Illustration of a conical flask partially filled with liquid.

What piece of apparatus is shown in the image above?

Conical flask

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The indicator methyl orange is in acidic solutions and in alkaline solutions. 

red
yellow

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Diagram showing a burette used in titration practicals.

What piece of apparatus is shown in the image above?

Burette

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What colour is phenolphthalein in acidic solutions? 

Red

Orange

Pink

Colourless

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Which piece of apparatus should you use to accurately measure the volume of your acid or alkali before transferring it to a conical flask?

Pipette 

Burette

Measuring cylinder 

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