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Titration - Using Conductivity.
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At the start of the titration
the conical flask contains
alkali
which
is fully ionised in water.
If electrodes are placed inside the conical
flask
the ions in the water will conduct electricity and a current will flow.
Conductivity
is a measure
of
how well the solution in the conical flask conducts
electricity.
The more ions there are
the better the conductivity and the higher
the
current will be.
The current can be measured using an ammeter.
As acid is added to the alkali
hydrogen ions and hydroxide
ions react together to form
water
molecules.
The number of ions in the conical
flask starts to decrease
and the current flowing through the
solution will be seen to decrease.
At neutralisation all of the hydrogen ions and hydroxide
ions
have reacted together to form water
molecules.
A neutral solution contains only salt ions dissolved in water
molecules.
The solution will still conduct electricity because of the
salt
ions
but the current will be at a minimum.
As more acid is added the current will start to
increase
because there will now be unreacted hydrogen ions in the solution
as well as the salt ions.
The solution is now no longer neutral but has become acidic.
If you draw a graph of current against the amount of acid added
you can see where the minimum is.
This is the end point of the
titration at neutralisation.
The titration can be repeated
with the same amounts of acid and alkali used
at the end point.
Pure salt crystals can then be crystallised from the neutral solution.
Headings
Acids and Alkalis Search
Questions 
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Copyright © 2008 Dr. Colin France. All Rights Reserved.