5b) Crude Oil

Crude Oil is a dark, smelly liquid which is a mixture of lots of different chemical compounds. A mixture contains two or more elements/ compounds that aren't chemically bond together.

Fractional Distillation:
-separates liquids with different boiling points

• Oil heated as it enters fractioning column 
• Chemicals in oil evaporate 
• Those with lowest boiling points evaporate first 
• They then condense to liquids 
• Lowest boiling point chemicals move further up the fractioning column 
• Liquid fractions drained off the column for use 

Fraction	Boiling Range	Viscosity	Use	Chain length
Refinery gases	lowest	lowest	bottled gases	Shortest C1 - C4
Gasoline			Petrol for cars	C5 - C9
Kerosine			Jet fuel	C12 - C15
Diesel			Fuel for cars/lorries	C15 - C20
Fuel oil			Fuel for ships	C21 upwards
Bitumen	highest	highest	Road buildings/ roofs	Longest around C30

Incomplete combustion can produce carbon monoxide which is dangerous because it reduces the capacity of the blood to produce oxygen.

Sulfur dioxide and nitrogen come from burning fuel. The sulfur dioxide comes from sulfur impurities in the fossil fuels. Nitrogen oxides are created when the temperature is high enough for the nitrogen and oxygen in the air to react. This often happens in car engines. Nitrogen monoxide and nitrogen dioxide are included in nitrogen oxide. 

Pollutants:

Acid rain is caused by sulfur dioxide and nitrogen oxides 

When sulfur dioxide mixes with the clouds it forms dilute sulfuric acid, which is much more acidic

2SO2(g) + O2(g) + 2H2O ---> 2H2SO4(aq) 

Nitrogen oxides can also form nitric acid in clouds, this rain is called acid rain. 

Acid rain causes lakes to become acidic and many plants and animals die as a result and it also kills trees and damages limestone buildings and ruins stone statues.

Cracking

Converts long chain alkanes in the heavier freactions into shorter chains that are currently in more demand. Also as a result an alkene is also produced which is used to make polymers.

Conditions for cracking

-In industry vapourised hydrocarbons are passed over a powered catalyst at about 600C - 700C. Silica (SiO2) and alumina (Al2O3) are used as catalysts.

1. heat the paraffin (or another alkane), after a few seconds move the bunsen burner to heat the catalyst. Alternate between the two until paraffin vapourises and catalyst glows red
2. heated paraffin cracks as it passes over catalyst 
3. small alkanes collected at end of boiling tube and alkene gases travel down the delivery tube 
4. Alkenes are collected through water using a gas jar