Links
Acids
and Alkalis
Revision Questions
gcsescience.com 30 gcsescience.com
What is an Indicator?
An indicator is a
substance that changes colour
at
the end point of a titration.
An indicator is added
to the solution in the conical
flask (see an example).
Different indicators
are used depending on
the strength
of the acid or alkali.
The indicator used for a particular
titration is given in the table below.
|
Indicators used for weak Acids or Alkalis. |
|||
| Indicator | Titration | Colour in Acid | Colour in Alkali |
| Methyl Orange | Strong Acid + Weak Alkali |
Red | Yellow |
| Phenolphthalein | Strong Alkali + Weak Acid |
Colourless | Pink |
Either Indicator can be used for a Strong Alkali + Strong Acid.
Universal
indicator is not usually used
for a titration because
it changes gradually giving different colours for a different pH.
Methyl orange or phenolphthalein are used
because they give a sudden change in
colour at neutralisation
which makes it easier to see the end point
of the titration.
Links
Acids
and Alkalis
Revision Questions
gcsescience.com The Periodic Table Index Neutralisation Quiz gcsescience.com
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