Volumetric AnalysisTopic 8.4

Titration readings• in a normal titration you are usually advised to

carry out at least one rough and two accurate titrations

• you should record your readings in a table like this Titration number 1 2 3 4

Final burette reading /cm3

25.2 24.8 33.3 24.9

Initial burette reading /cm3

0.0 0.0 7.4 0.1

Volume of NaOH used /cm3

25.2 24.8 25.9 24.8

Best titration results

In general, you should carry out as many titrations needed to obtain two or more consistent volumes

If no consistent volumes are obtained, the average value should be calculated

Titration number 1 2 3 4

Final burette reading /cm3

25.2 24.8 33.3 24.9

Initial burette reading /cm3

0.0 0.0 7.4 0.1

Volume of NaOH used /cm3

25.2 24.8 25.9 24.8

Best titration results

Suppose the following readings are obtained

Results

Mean volume of sodium hydroxide used is = 24.8 cm3

• Process of adding solvent to lower the concentration of a solution

M1V1 = M2V2

Dilutions

You have a stock solution of 15.8 M HNO3. How many mL of this solution should you dilute to make 100.0 mL of 0.250 M HNO3?

What safety rule should we remember when carrying out this procedure?

Proper Technique for Dilutions(implies being made from more concentrated solution)

1. Using pipette, transfer calculated amount of diluent to appropriate volumetric flask.

2. Add deionized water so that bottom of meniscus is at the marked line.

3. Cap to mix.

Proper Technique for Making Solution from a Solid

1. Using a balance, mass out appropriate amount of solid solute in weigh boat or weigh paper.

2. Carefully add to appropriate volumetric flask, being sure to rinse residual solute on weigh boat into flask.

3. Fill volumetric flask halfway with DI water then swirl to dissolve.

4. Finally, add deionized water so that bottom of meniscus is at the marked line.

5. Cap to mix.