Headings
Acids and Alkalis Search
Questions 
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.
Headings
Acids and Alkalis Search
Questions
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