Product details

Dissociation equilibrium with Cobra4

Dissociation equilibrium with Cobra4

Item no.: P3030960
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Experiment Type: Teacher Experiment, Laboratory Experiment

Difficulty Expenditure of Time print
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Carboxylic acids are potential electrolytes which exist in a weakly dissociated condition in aqueous solutions. The location of the dissociation equilibrium is quantitatively described by the Ka or pKa value which can be determined with potentiometric measurements.


  • Simplified implementation: all pre-settings already prepared
  • Drop counter optimizes the experimental procedure


  1. Measure the alteration of the pH value during a titration of approximately 0.1 molar aqueous solutions of formic acid, acetic acid, monochloroacetic acid, propionic acid, butyric acid and lactic acid with a 0.1 molar sodium hydroxide solution at constant temperature using Cobra4 system.
  2. From the neutralisation curves read the pKa values of the acids and compare them.

What you can learn about

  • True and potential electrolytes
  • Strong and weak acids
  • Law of mass action
  • Henderson-Hasselbalch equation
  • Dissociation constant and pKa value
  • Substituent effects
  • Potentiometry

Necessary accessories

  • Precision balance 620g/0.001g

Software included. Computer not provided.


Document     Filesize
p3030960e.pdf Experiment guide, English 541.24 KB

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