Hydrocarbons
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What are hydrocarbons?
Any compound formed from carbon and hydrogen atoms only
What is the general formula for alkanes?
CnH2n+2
What are alkanes?
• alkanes are saturated hydrocarbons meaning each carbon atom forms four single covalent bonds • the alkanes are a homologous series meaning they are a group of organic compounds that react in a similar way
What are the first 4 alkanes?
Methane, ethane,propane and butane
What is the formula for methane?
CH4
What is the formula for ethane?
C2H6
What is the formula for propane?
C3H8
What is the formula for butane?
C4H10
What impacts the properties of hydrocarbons?
The length of the carbon chain
The shorter the carbon chain of a hydrocarbon the ……. it is
-less viscous (more runny) -more volatile (lower boiling point) -more flammable (easier to ignite) • these properties make them good fuels
Why are hydrocarbons with shorter carbon chains better as fuels?
They are easier to ignite/ are more flammable
What reaction occurs during the complete combustion of hydrocarbons?
• hydrocarbon + oxygen—> carbon dioxide + water • during this reaction both hydrogen and carbon from the hydrocarbon are oxidised
What reaction occurs during the incomplete combustion of hydrocarbons?
Hydrocarbon+oxygen—> carbon monoxide + water + carbon
When does complete combustion occur?
When there is a good supply of oxygen
When does incomplete combustion occur?
When there is a poor supply of oxygen
Why are hydrocarbons used as fuels?
They are used as fuels due to the amount of energy released when they combust completely
Give an example of how the properties of hydrocarbons impact how they’re used for fuels?
Short chain hydrocarbons with lower boiling points are used as bottled gases- stored under pressure as liquids in bottles
Why are long chain carbon hydrocarbons not as good fuels?
They form viscous (gloopy) liquids like tar which aren’t as useful
Write a balanced equation for the complete combustion of methane (CH4)
CH4 + 2O2 —> CO2 + 2H2O
Why do hydrocarbons with longer chains have higher boiling points and melting points.
They have strong intermolecular forces between them which take a lot of energy to overcome