Dissociation equilibrium with Cobra4

p3030960i_35

Item no.: P3030960

Principle

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.

Tasks

  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.