Volumetric

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Rinse the burette and the pipette with the solutions to be used in them, to avoid dilution with water.

The burette tap must be tight to avoid leakage.

Remove the funnel from the burette before titration, to avoid an increase in the volume of the solution in the burette.

CONSULT YOUR TEXTBOOKS FOR MORE PRECAUTIONS

Slide 34

Recording in titration

Titration work could be recorded thus:

state the size of the pipette used in cm3

name the indicator used

record your titrations in tabular form as shown below

Slide 35

Find the average volume of acid used from any two or more titre values that do not differ by more than 0.20cm3 .This called concordancy

Rough titre may be used in averaging if it is within the concordant values.

Recording in titration

Slide 36

Indicator Selection for Titrations

Slide 37

Titration Calculations

Useful Information.

The concentration of one of the solutions, the acid for example (CA)

The volume of acid used for the titration (VA)

The volume of base used for the titration (VB)

What you will calculate:

The concentration of the other solution, the base for example (CB)

Slide 38

Details of the theory behind the calculations

Let’s work through this example:

During a titration 75.8 cm3 of a 0.100M standard solution of HCl is titrated to end point with 100.0 cm3 of a NaOH solution with an unknown concentration. What is the concentration of the NaOH solution.

Slide 39

The theory

Begin with a balanced equation for the reaction:

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) na = 1 nb = 1 (mole ratios of acid and base)

Mole = concentration X volume

For the acid: na = CaVa

For the base: nb = CbVb

na : nb (stoichiometry mole ratio)

CaVa : CbVb

Slide 40

The Theory

na : nb

CaVa : CbVb

i.e. na nb

CaVa CbVb

Then, CaVa na

CbVb nb

=

=

Slide 41

Tips on solving the problem

Convert the given conc. (base/acid) mol/dm3 to mol/given vol(base/acid).

If the conc. Is given in g/dm3, first convert to . mol/dm3 then to mol/given vol(base/acid).

Use the mole ratio and mol/given vol(base/acid)., get the mol/given vol.(acid/base).