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Crude Oil, shortest molecules, lowest boiling point, least viscous and…
Crude Oil
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catalytic cracking
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it is necessary as there are more long chain hydrocarbons are in less demand so are cracked into shorter chain hydrocarbons to meet the demand
NOTE - during a laboratory experiment of cracking alkanes, there is a danger water will rise up the delivery tube and into the hot test tube. To prevent this remove the delivery tube from the water BOFORE STOPPING HEATING
combustion
complete combustion - good supply of oxygen
- general reaction: hydrocarbon + oxygen → carbon dioxide + water
- word equation: methane + oxygen → carbon dioxide + water
- symbol equation: CH4 + 2O2 → CO2 + 2H2O
incomplete combustion - less oxygen available
- general reaction: hydrocarbon + oxygen → (carbon) + carbon monoxide + water
- word equation: methane + oxygen → (carbon) + carbon monoxide + water
- symbol equation: 2CH4 + O2 → 2CO + 4H2O
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definitions
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homologous series - a group of compounds with the same general formula and similar chemical properties
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fractional distillation
The Process
- crude oil is heated in a furnace and evaporates
- the vapours pass into the fractionating column, which is hottest at the bottom and cooler at the top (temp. gradient)
- long chain hydrocarbons have very high boiling points, so they cool down and condense towards the bottom of the column
- shorter chain hydrocarbons rise up the column as gases and condense at different heights so the mixture is separated on the basis of molecule size
- each different height is called a fraction
shortest molecules, lowest boiling point, least viscous and colourless
largest molecules, highest boiling point, most viscous and darkest