Titration Theory - Titration is a laboratory technique by which we can use to determine the concentration of an unknown solution using a standard concentration of another solution that chemically reacts with the unknown.

To find the morality of the unknown you use this formula;

                                     

Which can be rearranged to find the concentration of the unknown;

Generally we know the morality of the titrant since it is a standard solution. We also pre-measure the volume of the unknown. We then titrate with the standard from a burette into the container with the measured unknown and the chemical indicator until the indicator either turns colour or a precipitate indicates that the end point or the equivalence point has been reached. Having the initial and final readings of the titrant burette gives us the volume of the titrant used. The only unknown in the above equation is the Normality of the unknown. 

Making the standard solution of sodium hydroxide

Theory

A standard solution is one whose concentration is known precisely. These are important because they can be used to find the concentration of other solutions by titration. It is very important to be able to make a reliable standard because if the standard is wrong no matter how carefully you carry out your titration your results will be wrong.

Method

 

1. work out how much sodium hydroxide is needed.
2. In practice it is time consuming and often impossible and unnecessary  to weigh out exactly the right amount of solid . Any think give of take 10% of the weight will do.
3. add about half the final amount of water into a beaker with the solid and stir in the beaker until completely dissolved.
4. transfer into the 250cl3 conical flask including all risings of the beaker and the glass rod so none of the ions are lost.
5. top up the conical flask to within 1cm of the line, stopper, and inverse several times to mix. Leave to settle tapping if necessary to get rid of bubbles
6. very carefully top up the conical flask until the meniscus sits exactly on the line like this:

 

7. stopper and mix again. The standard is now ready.
8. work out the actual concentration using the formula:

Results    

Final concentration of standard = 0.092 moldm-3 

Using my standard sodium hydroxide solution for titration

Diagram

Method

1. rinse the burette first with water and then with a little of the solution to be used. And then fill it with taw standard.
2. put 25cm3 of the unknown into a conical flask with a pipette and add 3-5 drops of indicator.
3. record the start reading
4. titrate until the indicator changes colour permanently
5. record the end reading.
6. rinse out the conical flask. Pipette in some more unknown and repeat as many times as needed until two results are within 0.1cm3  of each other.

Results

 

Conclusion