4.5 - Organics I Flashcards
What is the general formula for alkanes?
CnH2n+2
What are alkanes?
homologous series of organic molecules (hydrocarbons)
Order of alkanes with increasing no. Carbons
-Methane
-Ethane
-Propane
-Butane
-Pentane
Alkanes have similar…
chemical reactions
Alkanes have trends in…
physical properties (e.g. BP, colour)
What are isomers?
molecules with the same formula but different structural formula
What is the general equation for complete combustion?
alkane + oxygen —> carbon dioxide + water
When does complete combustion occur?
excess of oxygen
When does incomplete combustion occur?
not enough oxygen
What are the products of incomplete combustion?
-carbon monoxide (CO)
-soot (C)
Why are alkanes combusted?
to release energy - most alkanes are used as fuels
Why is carbon monoxide harmful?
-toxic gas
-lowers oxygen-carrying capacity of blood
Why is soot harmful?
-causes lung disease
Incomplete combustion releases less…
energy - LESS USEFUL
Wat are the 2 pollutants that are released as a result of combustion?
-carbon dioxide
-sulphur dioxide
Why is carbon dioxide harmful?
-greenhouse gas
-traps heat in the atmosphere, causes climate change
Why is acid rain harmful?
-corrodes structures
-harmful to plant and aquatic life
How is sulphur dioxide formed as a result of combustion?
when sulphur impurities in the fuel combust
Why is sulphur dioxide harmful?
acid rain
What is an alkane reaction with a halogen an example of?
substitution reaction
What does a halogen reaction with an alkANE require?
UV light
What happens in a halogen and alkane reaction?
hydrogen swaps with a halogen (e.g. chlorine)
Why do we use cracking?
to break down longer alkanes into useful, shorter ones
What are the 2 cracking conditions?
-temp (650C)
-catalyst (aluminium oxide)
