Practical 5: Distillation of a product from a reaction
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What is the general reaction focused on during practical 5?
The reaction involving the formation of an aldehyde from the oxidation of an alcohol
What type of reaction is oxidation of a primary alcohol to an aldehyde?
A partial oxidation reaction
Role of acidified potassium dichromate (VI) in the reaction?
Acts as an oxidising agent
What colour change is observed when alcohol is oxidised by dichromate (VI)?
Solution changes from orange to green
Why is the reaction mixture heated under distillation rather than reflux when preparing an aldehyde?
To allow the aldehyde to distil off before further oxidation to a carboxylic acid
Purpose of anti - bumping granules during heating?
To promote smooth boiling and prevent violent bubbling
Why should the condenser be placed at a downward angle in distillation?
So the condensed liquid can flow easily into the receiving flask
Function of the thermometer in the distillation setup?
To monitor the temperature of the vapour, indicating which substance is distilling
How can the identity or purity of the distilled product be checked?
By measuring its boiling point and comparing it to the known value
Why must distillation be stopped once the desired temperature range is reached?
To prevent further oxidation or collection pf unwanted by - products
Purpose of refluxing instead of distilling when making a carboxylic acid?
Reflux allows complete oxidation y heating the mixture without losing volatile components
Why should the apparatus not be sealed during distillation?
To avid build - up which could cause the apparatus to explode
How can residual water in the distillate be removed?
By drying with anhydrous salt (CaCl2 or MgSO4)
Why might the yield of the distillation be less than expected?
Product loss during transfer Reaction is incomplete Volatile components evaporate
How can yield be improved in this practical?
1.Distill slowly 2. Cool the condenser efficiently to maximise collection