Determination of acidity (pKa value) by titration

Determination of acidity (pKa value) by titration
Determination of acidity (pKa value) by titration

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In experiment C1.7.2.1, the acidity (pKa value) of acetic acid is determined. Between an acid HA and its base A- the following equilibrium reaction takes place in an aqueous solution :

According to the law of mass action, the equilibrium position is described by the equilibrium constant Ka:

By analogy to the pH value, the pKa value is given as the negative base 10 logarithm of the numerical value of Ka

The lower the value of pKa, the higher the acidity. The pKa value is numerically equal to the pH value of a solution when the protonated and non-protonated forms are present in equal concentration.

Components of equipment sets

1 524005W2 Mobile-CASSY 2 WiFi LD
1 524220  4  CASSY Lab 2 LD
1 5240672  4  pH adapter S LD
1 6674172  4  pH sensor with plastic shaft, BNC LD
1 607105  8  Magnetic stirrer mini LD
1 666851  4  Stirring magnet, 25 mm x 6 mm Ø, circular LD
1 665845  4  Burette side stopcock, 25 ml LD
1 666559  8  Burette clamp for 1 burette, roller clamp LD
1 665816  4  Burette filling funnel plastic, 35 mm Ø LD
1 30002  4  Stand base, V-shaped, small LD
1 30043  8  Stand rod, 75 cm, 12 mm diam. LD
1 30126  4  Stand rod 25 cm, 10 mm Ø LD
1 30011  4  Saddle base LD
1 30109  4  Bosshead S LD
1 666555  4  Universal clamp 0...80 mm LD
1 665997  4  Graduated pipette 10 ml LD
1 666003  4  Pipetting ball (Peleus ball) LD
1 664130  4  Beaker, Boro 3.3, 250 ml, squat LD
1 661243  4  Wash bottle PE 500 ml LD
1 6610821 Stopcock grease LD
1 6719560  4  Acetic acid, 0.1 mol/l, 500ml LD
1 6738410  4  Sodium hydroxide solution, 0.1 mol/l, 500ml LD
GHS05 Warning H290
1 6742500  4  Phenolphthalein solution, 100 ml LD
GHS02GHS07 Danger H225 H319
1 6744640  4  Buffer solution pH 4.00, 250 ml LD
1 6744670  4  Buffer solution pH 7.00, 250 ml LD
1 6753400  4  Water, pure, 1 l LD
1 additionally required: PC with Windows 7 or higher with WIFI or USB connection

Experiment Instructions

PDF (Experiment description) PDF (Experiment description) C1.7.2.1 Determination of acidity (pKa value) by titration
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