Hydrocarbons from Crude oil

1. Hydrocarbons from Crude oil Define crude oil as being a source of a variety of different length hydrocarbons (of varying use) Explain how different hydrocarbons are separated using FRACTIONAL DISTILLATION Explain, in terms of Van Der Waals’ forces, the trend in boiling point of different length hydrocarbons

2. How was crude oil made? Crude oil is thought to have been made from the remains of marine plants and animals that died millions of years ago. These remains sank to thebottom of the sea, where theywere buried in layers of sand andmud, preventing them from rotting. These layers gradually became sedimentary rock. Over millions of years the layers of rock built up, increasing the heat and pressure. This caused the remains to be broken down into the molecules that form crude oil and natural gas.

3. Hydrocarbons in crude oil Crude oil is a mixture of over 150 different hydrocarbons. Most of them are unbranched (straight-chained) alkanes. Crude oil is not very useful in its native state as it does not ignite easily. However, individually, the components of crude oil have a variety of uses...if they can be separated out!

4. Fractional Distillation Fractional distillation is a process used to separate a mixture of liquids that have different boiling points. When the mixture is heated, liquids with a low boiling point evaporate and turn to vapour. Liquids with a higher boiling point remain as liquid. The vapour can then be separated from the liquid.

5. How does fractional distillation work?

6. How does fractional distillation work? near the top. condense at different levels of the fractionating different fractions of crude oil according to their boiling points. a fractionating column where becoming a vapour. the column is hotter at the bottom than the top. the oil cools down and condenses. Each fraction of the crude oil will whereas fractions with This vapour is passed into crude oil until it evaporates, point will condense near the bottom, Fractions with a higher boiling process of separating out Fractional distillation is the It begins by heating up column, depending on their boiling point, as a lower boiling point will condense

7. How does fractional distillation work? ANSWERS Fractional distillation is the process of separating out different fractions of crude oil according to their boiling points. It begins by heating up crude oil until it evaporates, becoming a vapour. This vapour is passed into a fractionating column where the oil cools down and condenses. Each fraction of the crude oil will condense at different levels of the fractionating the column is hotter at the bottom than the top. column, depending on their boiling point, as Fractions with a higher boiling point will condense near the bottom, whereas fractions with a lower boiling point will condense near the top.

8. Boiling point of alkanes

9. Van der Waals’ forces Weak intermolecular forces that must be broken for a liquid to boil. As the chain length increases there are more points of contact between the molecules leading to more Van der Waals’ forces. It therefore takes more energy (higher temp) to overcome these forces.

10. Effect of branching Branched isomer will have a lower boiling point than the unbranched isomer. There are fewer points of contact between molecules, therefore fewer Van der Waals’ forces.