12 Chemistry 2.2 quantitative chemistry CR 07
Titrations Titrations are
used to measure exact amounts of reactants in a reaction and use the information to find unknown concentrations.
12 Chemistry 2.2 quantitative chemistry CR 07
Titration Equipment
Electronic Balance
-used to accurately weigh solute
12 Chemistry 2.2 quantitative chemistry CR 07
Volumetric Flask
- used to make exact volumes of solution
12 Chemistry 2.2 quantitative chemistry CR 07
Pipette -used to
measure and transfer a known volume of solution
12 Chemistry 2.2 quantitative chemistry CR 07
Conical flask
- used to mix solutions
(reaction vessel)
12 Chemistry 2.2 quantitative chemistry CR 07
Burette - used to exactly
measure the volume of solution that has reacted –this is known as the titre
12 Chemistry 2.2 quantitative chemistry CR 07
From known to unknownIn a titration a known volume of solution with a known concentration is used to react with a solution of unknown concentration. Using c = n/v the unknown concentration can be calculated.
12 Chemistry 2.2 quantitative chemistry CR 07
The known – standard solution
Making a solution of known concentration is done by Measuring an exact mass of solute and mixing it with an exact volume of water in a volumetric flask.
12 Chemistry 2.2 quantitative chemistry CR 07
Making a Standard Solution
1. Weigh solute exactly
2. Mix in beaker with distilled water
3. Pour into volumetric flask
12 Chemistry 2.2 quantitative chemistry CR 07
4. Rinse beaker into volumetric flask with distilled water
5. Mix by swirling volumetric flask
12 Chemistry 2.2 quantitative chemistry CR 07
6. Make the volume up to the exact amount by adding water drop by drop
The volumetric flask must be on a flat surface and at eye level.AND the bottom of the meniscus
must sit on the line.
12 Chemistry 2.2 quantitative chemistry CR 07
Standard solution
If the solution level goes over the line on the neck of the volumetric flask then the solution is no longer a standard solution and the whole process must start again.
12 Chemistry 2.2 quantitative chemistry CR 07
Transferring
A pipette is used to transfer the set volume of the solution to the reaction vessel (conical flask).
*eye level
12 Chemistry 2.2 quantitative chemistry CR 07
Emptying the pipette
1. Touch end of pipette on side of vessel
2. There should be some liquid left in the bottom
12 Chemistry 2.2 quantitative chemistry CR 07
Aliquots
The measured amount of solution that is transferred to the conical flask is called an aliquot.
Indicator is added to the aliquot so that end point of the reaction can be determined.
12 Chemistry 2.2 quantitative chemistry CR 07
Burette The burette is rinsed with the solution it will contain and then filled and read at eye level
12 Chemistry 2.2 quantitative chemistry CR 07
The ReactionThe reaction occurs in the conical flask, which is swirled gently under the tap. After a ‘rough’ titration has been done solution is added drop-wise when near the end point.
12 Chemistry 2.2 quantitative chemistry CR 07
Titrations
Known usually goes into burette and unknown into conical flask
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