3.3.2.1. Fractional Distillation of crude oil Flashcards
At room temperature:
C1-C5 is gas
C5-C17 is liquid
>C17 is a waxy solid
What are the other physical properties of alkanes?
Non-polar (low difference in electronegativity between C and H)
Have Van der Waal forces acting only between molecules, so as chain length increases Van der Waal forces get stronger, so more energy needed to overcome forces so m.p./b.p. increases
Why do branched chain isomers have different melting/boiling points?
They have lower melting/boiling points than straight chain molecules because branched chains cannot pack as close together, so smaller surface area in contact with each other. so weaker Van der Waal forces so m.p./b.p. decreases
What are other random properties of alkanes?
Do not dissolve in polar substances e.g. water but do in non-polar e.g. cyclohexane. (like dissolves like)
Fractional distillation separates crude oil (mixture of alkanes) (?)
Water and alkane mixture can be separated using a separating funnel.
What is crude oil?
A main source of organic materials and is dark yellow/black, sticky, viscous liquid
How is crude oil formed?
Plankton died. Over time, it was buried under mud and sediment, the high temperatures and pressure cause the plankton to be transformed into crude oil over millions of years. Crude oil is a mixture of hydrocarbons (alkanes)
What are the fractions in order (Bottom to top)
Bitumen, Heavy fuel oil, Paraffin, Diesel, Kerosene, Naphtha, Petrol, LPG
Describe the process of fractional distillation
- Vapourise crude oil
- Vapour enters the fractionating column
- There is a negative temperature gradient in the column (bottom is hot, top is cooler)
- The alkanes in crude oil have different length chains, so have different boiling points, so will condense at different levels.
- Heavy fractions (long chained) condense at the bottom, light fractions (shorter chained) condense at the top
*each fraction is still a mixture of alkanes
