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