12.2 Fractional distillation of crude oil

Question 1

What functional group make up crude oil

Answer 1

Alkanes, branched and unbranched

It may also contain small amounts of other compounds eg sulfur dissolved in it that come from other elements in the plants and animals that form it.

Question 1

Why is crude oil a fossil fuel
How is it made

Answer 1

it was formed millions of years ago by the breakdown of animal and plant remains

At high pressures deep below the earths surface

So because it forms very slowly, it is non - renewable

Question 2

How can acid rain be formed from burning crude oil

Answer 2

There can be impurities eg small amounts of other compounds eg sulfur in it

When sulfur is burned, it produces sulfur dioxide

This sulfur dioxide reacts with oxygen high in the atmosphere to form sulfur trioxide.
This reacts with water in atmosphere to form sulfuric acid which leads to acid rain

Question 3

Why is crude oil fractionated

Answer 3

. To get it into useful products you have to separate the mixture
This is done by heating it and collecting the fractions that boil over different ranges of temperatures

So each fraction is a mixture of hydrocarbons at similar chain lengths which therefore have similar properties

Question 4

Describe process of fractional distillation

Answer 4

• Crude oil is heated in a furnace
• A mixture of liquid and vapour passes into a fractionating tower that is cooler at the top and hotter at the bottom
• The vapours pass up the tower via a series of trays containing bubble caps until they arrive at a tray that is cool so they condense to liquid
• The mixture of liquids that condense at each tray is piped off
• The shorter chain hydrocarbons condense in the trays nearer to the top of the tower where it is cooler as they have lower boiling points
• The thick residue that collects at the base of the tower is called tar or bitumen
  It can be used for road surfacing, or it is further processed to give more valuable products

Question 5

What is fracking

Answer 5

. When there methane gas stuck in shale rock, so the gas is extracted by drilling into the rock, and forcing pressurised water mixed with sand into it

. This releases the trapped methane gas which flows to the surface

Question 6

Why do people oppose fracking

Answer 6

. May cause small earthquakes
. Burning a natural gas produces CO2 which is a cause of global warming
. Waste of water
. Chemical additives pollute water supplys