*
Sulfuric acid is very corrosive, * Chromium compounds are poisonous. *Experiemnt
for a chemistry teacher. * Use atray. * Do not forget your goggles!
During oxidation
of ethanol (methylated spirit) with acidic potassium dichromate solution
each ethanol molecule splitted off two H-atoms resulting in the formation
of ethanal.
In the following experiment
you will take primary, secondary and tertiary butanol to learn about isomerism.
What
you need:TDropper bottles with
primary, secondary, tertiary butanole, concentrated sulfuric acid, diluted
potassium dichromate solution, three small injection bottles.
Experiment:*
Take the three bottles to mix one drop of each of the butanol samples with
3 drops of the potassium dichromate solution. * Add 1 drop of concentrated
sulfuric acid to each of the samples and mix.
Observation
Right
photo:
The orange colour of dichromate
ions only disappears in the samples of primary and secondary butanol.
It is replaced by the blueish colour of chromium ions.
Explanation:
Molecules of primary and secondary alcohols are electron donors in direct
redox reactions, dichromate ions are electron acceptors. The blueish colour
indicates chromium ions (Cr3+(aq)).