C1 Distillation (page 102) Flashcards
What is Distillation?
Distillation is used to separate mixtures which contain liquids
What two types of Distillation is there?
Simple and Fractional
What is ‘Simple’ Distillation used for?
Simple distillation is used for separating out a liquid from a solution
Describe the process of ‘Simple Distillation’
1) The solution is heated (the part of the solution that has the lowest boiling point evaporates first
2) The vapour is then cooled, condences (turns back into a liquid) and is collected.
3) The rest of the solution is left behind in the flask.
What can you use ‘Simple Distillation’ to get?
Pure water from sea water
How do simple distillation get pure water from sea water?
The water evaporates and is condened and collected.
Eventually you’ll end up with just the salt left in the flask.
What is the problem with ‘simple Distillation’?
the problem is that you can only use it to separate things with very different boiling points - If the temperature goes higher than the boiling point of the substance with the higher boiling point, they will mix again
If you have a mixture of liquids with similar boiling points, can you use ‘simple distillation?
No you need another method to separate them - like fractional distiallation
what is Fractional Distillation?
It is used to separate a mixture of liquids
What is the process of fractional distillation of crude oil?
Put your mixture in a flask and stick a Fractionating Column on the top (look at page 102 in your book at diagram).
The different liquids will all have different boiling points - so they will evaporate at different temperatures.
The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column.
Liquids with higher boiling points might also start to evaporate. But the column is cooler towards the top. So they will only get part of the way up before condensing and running back down towards the flask.
When first liquid has been collected, you raise the temperature until the next one reaches the top.
Propan-l-ol, methanol and ethanol have boiling points of 97°C, 65°C and 78°C respectively. A student uses fractional Distillation to separate a mixture of these compounds. State which liquid will be collected in the second fraction and explain why?
Ethanol
Ethanol has the second lowest boiling point and will be collected once all the methanol has been distilled off and the temperature increased.
