4.7: Know that Crude Oil is a Mixture of Hydrocarbons

CRUDE OIL: Mixture of Hydrocarbons - thick, sticky, black liquid that is found under porous rock (under the sea)

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Diagram:

 



 

Diagram showing where Crude Oil is found

4.8: Describe How the Industrial Process of Fractional Distillation Separates Crude Oil into Fractions

CRUDE OIL: Mixture of Hydrocarbons

FRACTIONAL DISTILLATION: Method to separate two or more liquids that are miscible with one another

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INDUSTRIAL PROCESS OF FRACTIONAL DISTILLATION:

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FRACTIONAL DISTILLATION OF CRUDE OIL

Diagram showing the Process of Fractional Distillation to Separate Crude Oil in a Fractionating Column

EXPLANATION: Fractional distillation is carried out in a fractionating column In the fractionating column, it is hot at the bottom and cool at the top Crude oil is transported into the fractionating column and heated into vapours that rise and evaporate Vapours of Hydrocarbons with high boiling points will immediately turn into liquid at the bottom of the column where they will be tapped off Vapours of Hydrocarbons with low boiling points will rise up the column and condense at the top where they will be tapped off Hence, different fractions will condense and be tapped off at different heights along the fractionating column according to their boiling points

4.9: Know the Names and Uses of the Main Fractions Obtained from Crude Oil: Refinery Gases, Gasoline, Kerosene, Diesel, Fuel Oil and Bitumen

CRUDE OIL: Mixture of Hydrocarbons - thick, sticky, black liquid that is found under porous rock (under the sea)
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DIFFERENT FRACTIONS OBTAINED FROM CRUDE OIL AND THEIR USES:

                        

Diagram showing the Different Fractions and their Main Uses

4.10: Know the Trend in Colour, Boiling Point and Viscosity of the Main Fractions

CRUDE OIL: Mixture of Hydrocarbons - thick, sticky, black liquid that is found under porous rock (under the sea)

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DIFFERENT FRACTIONS OBTAINED FROM CRUDE OIL:

              

TRENDS IN FRACTIONS OBTAINED:

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4.11: Know that a Fuel is a Substance that, When Burned, Releases Heat Energy

FUEL: Substance burned to releases heat energy to be used as an energy source

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• Heat energy is transferred into electricity (electrical energy) used in our daily lives

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Examples:

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Picture showing Oil, Coal and Natural Gases - Common Fossil Fuels

4.12: Know the Possible Products of Complete and Incomplete Combustion of Hydrocarbons with Oxygen and Air

COMBUSTION: Chemical reaction that involves burning

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COMPLETE COMBUSTION: Chemical reaction that involves burning with an unlimited supply of Oxygen so elements in fuel fully react with Oxygen

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COMPLETE COMBUSTION OF HYDROCARBONS:

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During the complete combustion of Hydrocarbons, Carbon Dioxide and Water will be produced:

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• Carbon will oxidise to form Carbon Dioxide
• Hydrogen will oxidise to Water

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EQUATION:

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Hydrocarbon   +   Oxygen   →   Carbon Dioxide   +   Water

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*INCOMPLETE COMBUSTION: Chemical reaction that involves burning with a limited supply of Oxygen so elements in fuel does not fully react with Oxygen

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INCOMPLETE COMBUSTION OF HYDROCARBONS:

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During the incomplete combustion of Hydrocarbons, Carbon Monoxide and Water will be produced:

• Carbon is released as soot
• Carbon Monoxide is a poisonous Gas that reduces the capacity of red blood cells (haemoglobin) to carry Oxygen

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EQUATION:

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Hydrocarbon   +   Oxygen   →   Carbon Monoxide   +   Water

4.13: Understand Why Carbon Monoxide is Poisonous, In Terms of its Effect on the Capacity of Blood to Transport Oxygen

CARBON MONOXIDE: Poisonous, colourless and odourless Gas that is produced during incomplete combustion

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Hydrocarbon   +   Oxygen   →   Carbon Monoxide   +   Water

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EFFECT OF CARBON MONOXIDE ON BLOOD:

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• When Carbon Monoxide is produced from incomplete combustion and inhaled into the lungs, it binds irreversibly to Haemoglobin in red blood cells
• As a result, this reduces the capacity of red blood cells to carry Oxygen

Diagram:

Diagram showing Carbon Monoxide Atoms

4.14: Know that, In Car Engines, the Temperature Reached is High Enough to Allow Nitrogen and Oxygen from Air to React, Forming Oxides of Nitrogen

FORMATION OF OXIDES OF NITROGEN IN CAR ENGINES:

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• IfCombustion of fuels in car engines causes high temperatures to be reached, allowing Nitrogen and Oxygen from the Air to combine to produce Nitrogen Monoxide:

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Nitrogen   +   Oxygen   →   Nitrogen Monoxide

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• When Nitrogen Monoxide is released from the exhaust of car engines, it combines with Oxygen in the Air to form Nitrogen Dioxide:

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Nitrogen Monoxide   +   Oxygen   →   Nitrogen Dioxide

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• Hence, both Nitrogen Monoxide and Nitrogen Dioxide are produced in car engines - referred to as NOx

4.15: Explain How the Combustion of Some Impurities in Hydrocarbon Fuels Results in the Formation of Sulfur Dioxide

HYDROCARBON FUELS: Impure hydrocarbon fuels that contain Sulfur compounds

COMBUSTION OF HYDROCARBON FUELS:

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• During combustion of Hydrocarbon fuels, impurities including Sulfur compounds will be oxidised to produce Sulfur Dioxide:

Sulfur   +   Oxygen   →   Sulfur Dioxide

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sEFFECTS OF SULFUR DIOXIDE:
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• Sulfur Dioxide released into the atmosphere will dissolve in Water droplets of clouds to make it more acidic (lower ph), resulting in Acid Rain

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EFFECT	EXPLANATION
Kills plants and trees	Leaches minerals and nutrients out of the soil, causing plants and trees to die
Kills aquatic organisms	Rivers and lakes become too acidic which causes aquatic organisms to die
Reduced plant and tree growth	Damages waxy layer of leaves, making it difficult for trees to absorb mineral ions needed for growth
Destroys buildings	Corrodes metals (steel) and limestone in buildings

4.16: Understand How Sulfur Dioxide and Oxides of Nitrogen Oxides Contribute to Acid Rain

ACID RAIN: Rain with low pH due to presence of dissolved acidic gases such as Sulfur Dioxide and Oxides of Nitrogen

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CONTRIBUTION OF SULFUR DIOXIDE AND OXIDES OF NITROGEN OXIDE TO ACID RAIN:

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Sulfur Dioxide will react with Oxygen and dissolve in Water droplets of Clouds to form dilute Sulfuric acid, causing acid rain:

Sulfur Dioxide   +   Oxygen   +   Water   →   Sulfuric Acid

Oxides of Nitrogen Oxides will dissolve in Water droplets of clouds to form dilute Nitric acid and Nitrous acid, causing acid rain:

Nitrogen Dioxide   +   Water   →   Nitric Acid

4.17: Describe How Long-Chain Alkanes are Converted to Alkenes and Shorter-Chain Alkanes by Catalytic Cracking (Using Silica or Alumina as the Catalyst and a Temperature in the Range of 600-700°C)

LONG - CHAIN HYDROCARBONS: Hydrocarbons with large number of hydrocarbon molecules

SHORT - CHAIN HYDROCARBONS: Hydrocarbons with small number of hydrocarbon molecules

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CONVERSION OF ALKANES TO ALKENES:

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CATALYTIC CRACKING

Picture showing Industrial Catalytic Cracking

EXPLANATION: Cracking breaks down large hydrocarbon molecules into smaller hydrocarbon molecules that are more useful, hence breaking down long-chain hydrocarbons into short-chain hydrocarbons Fractions containing large hydrocarbon molecules (long-chain hydrocarbons) are heated and vaporised at 600 - 700°C Vapours will then pass over a hot catalyst of Silica or Alumina, breaking down covalent bonds in molecules which causes thermal decomposition to occur As a result, cracking produces smaller Alkanes and Alkenes

4.18: Explain Why Cracking is Necessary, in Terms of the Balance Between Supply and Demand for Different Fractions

LONG - CHAIN HYDROCARBONS: Molecule with large number of hydrocarbon molecules

SHORT - CHAIN HYDROCARBONS: Molecule with small number of hydrocarbon molecules

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WHY CRACKING IS NECESSARY:

• Although each fraction obtained from the fractional distillation of crude oil is useful, more long-chain hydrocarbons are produced than needed
• However, less short-chain hydrocarbons are produced than needed (e.g gasoline fraction) as there is a higher demand for short-chain hydrocarbons to be used as polymers for plastic, gasoline, and petrol for cars
• Hence, cracking is necessary to provide for the insufficient supply of short-chain hydrocarbons

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Example: Cracking of Decame ( C10H22 ) to produce Octane ( C8H18 ) and Ethene

( C2H4 ) :

C10H22 (g)    →    C8H18 (g)    +    C2H4 (g)

Octane : Octane produced can be used to make Petrol

Ethene : Ethene can be used to make Poly (Ethene) - a type of plastic