| time
requ.: |
20 minutes. |
|
objective: |
Properties of
alcohols. |
| material: |
- 3 teat pipettes
- 6 test tubes d=18mm
- 3 test tubes d=30mm
- glass rod
- boiling stones
|
- beaker 50ml
- scales
- spatula
- thermometer T<120°C
- test tube holder (for 30mm)
|
| chemicals: |
- ethanol
- 1-propanol
- 1-butanol
|
- nitric acid c=2mol/l
- ceric ammonium nitrate
- sodium chloride solution
c=3mol/l
|
|
preparation: |
Note: adapt
volume of stock solution to the estimated number of tests you plan. For
about 30 tests: Prepare a
stock solution of reagent by dissolving 10g ceric ammonium nitrate in 25ml
of the nitric acid. |
|
procedure 1: |
Dilute 1ml reagent with 2ml water. Add 5 drops
of the unknown sample and shake.
|
|
observation 1: |
The colour changes from yellow to orange/red.
|
|
interpretation 1: |
The compounds
contain an alcoholic group. |
|
procedure 2: |
Test the
solubility of the 3 alcohols in water and in salt water: shake 2ml alcohol and 2ml solvent in a test tube
and observe solubility. |
|
observation 2: |
complete
solubility in water: ethanol, propanol
complete solubility in salt water: ?
incomplete solubility in water: butanol
incomplete solubility in salt water: ? |
|
interpretation 2: |
The length of
the hydrocarbon part of the molecule increases. |
|
procedure 3: |
Boiling
temperature: give about 5ml alcohol, a boiling
stone and a thermometer in a large test tube and heat until the liquid
is boiling. Take the test tube out of the flame and measure the
temperature: it approximately represents the boiling point. |
|
observation 3: |
(Lit.: ethanol=78°C
propanol=97°C butanol=117°C) |
|
interpretation 3: |
Discuss the
results in terms of intermolecular interactions. |
|
disposal of: |
Organic
solvents. |
|
source: |
Barke, H.-D. et al.: One Hundred
Chemistry-Experiments to Avoid Chalk and Talk; University of Muenster,
2004. |
