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.
Benefits
- Simplified implementation: all pre-settings already prepared
- Drop counter optimizes the experimental procedure
Tasks
- 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.
- 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.
Scope of Supply
| Device Name | Item no. | Qty |
|---|
| curricuLAB measureLAB, multi-user license | 14580-61 | 1,00 |
| Monochloroacetic acid 100 g | 30060-10 | 1,00 |
| Magnetic stirring bar 15 mm, cylindrical | 46299-01 | 1,00 |
| Right angle boss-head clamp | 37697-00 | 3,00 |
| Water, distilled 5 l | 31246-81 | 1,00 |
| Holder for sensors with support rod | 12680-00 | 2,00 |
| Beaker, Borosilicate, tall form, 50 ml | 46025-00 | 2,00 |
| Pasteur pipettes, 250 pcs | 36590-00 | 1,00 |
| Wash bottle, plastic, 500 ml | 33931-00 | 1,00 |
| Lactic acid 100 | 30264-10 | 1,00 |
| Caustic soda sol.,0.1M 1000 | 48328-70 | 1,00 |
| Burette clamp, roller mount., 2 pl. | 37720-00 | 1,00 |
| Volumetric flask, Borosilicate, 100 ml, IGJ12/21 | 36548-00 | 6,00 |
| Acetic acid 99...100%, pure 1 | 31301-70 | 1,00 |
| Immersion probe NiCr-Ni, teflon, 300 °C | 13615-05 | 1,00 |
| Beaker, Borosilicate, tall form, 250 ml | 46027-00 | 1,00 |
| Pipettor | 36592-00 | 1,00 |
| Magnetic stirrer without heating, 3 ltr., 230 V | 35761-99 | 1,00 |
| Buffer solution, pH 4.62 1000 | 30280-70 | 1,00 |
| Cobra4 Sensor-Unit Chemistry | 12630-00 | 1,00 |
| Rubber stopper,d=18/14mm, 1 hole | 39254-01 | 1,00 |
| Volumetric pipette, 5 ml | 36577-00 | 6,00 |
| Propionic acid, 500 | 31753-50 | 1,00 |
| N-butyric acid 100 | 30047-10 | 1,00 |
| pH-electrode, plastic body, gel, BNC | 46265-15 | 1,00 |
| Retort stand, h = 750 mm | 37694-00 | 1,00 |
| Beaker, DURAN®, tall form, 150 ml | 36003-00 | 1,00 |
| Buffer solution, pH 9 1000 | 30289-70 | 1,00 |
| Rubber caps, 10 pcs | 39275-03 | 1,00 |
| Pipette dish | 36589-00 | 1,00 |
| Microspoon, steel | 33393-00 | 1,00 |
| Burette, lateral stopcock, Schellbach, 25 ml | MAU-24022021 | 1,00 |
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