Hydrocarbons Flashcards
A fuel is a substance which ….
Releases energy when burned.
When hydrocarbons are burnt in oxygen they produce…
carbon dioxide and water
If hydrocarbons burn with insufficient oxygen, what is produced?
Carbon monoxide and water
Why is carbon monoxide poisonous?
CO combines with red blood cells reducing their capacity to carry oxygen.
Some fuels contain sulfur. What other gas is produced when they are burned?
Sulphur dioxide
When sulfur dioxide is released into the air it combines with moisture and oxygen to form……
Acid rain
High temps in car engine can cause nitrogen and oxygen to combine to form….
Nitrogen oxides
Nitrogen oxide and sulfur dioxide both contribute to ….
Acid rain
Acid rain can cause what problems?
Lakes and streams become acidic and kill plants and fish
Releases ions into the soil which are poisonous to trees and destroys forests
How many bonds does carbon form?
4
How many bonds does hydrogen form?
1
When a hydrocarbon only has single bonds the compounds are called…
Alkanes
The first 5 members of the alkanes are
n= 1 Methane. Monkeys eat peeled bananas. n=2 Ethane. n=3 Propane n=4 Butane n=5 Pentane
Alkanes are saturated hydrocarbons with single bonded carbon.
The general formula for alkanes is …..
C (n) H (2n+2)
What is an Isomer?
Isomers are compounds which have the same molecular formula but different structural formula
In combustion, alkanes burn in air to produce ….
CO2 carbon dioxide
H2O water
Do hydrocarbons have ionic or covalent bonding?
Covalent
Why don’t hydrocarbons take part in many chemical reactions?
Strong covalent bonds so difficult to break
Hydrocarbons react with 2 halogens which are…
Bromine and chlorine (alkanes need uv light to react)
A Substitution reaction
Definition of an alkene
- An alkene is a hydrocarbon that contains a double bond
- It is unsaturated as the double bond can split so the carbon can join with other atoms.
Alkenes are unsaturated hydrocarbons. Does this make them more or less reactive than alkanes?
More reactive and so more useful
What is the general formula for alkenes?
C n H 2n
What is a hydrocarbon?
Molecules made up of hydrogen and carbon atoms only
What does saturated mean?
The carbon atoms cannot bond with any more atoms
What does unsaturated mean?
Unsaturated hydrocarbons can make more bonds.
The double bond splits and joins with other atoms. Like in alkenes.
What colour change does bromine water have when you add an alkene?
Bromine after turns orange to colourless
What three characteristics of the compounds in a homologous series have?
- Have same general formula
- Similar chemical properties
- Gradual change in physical properties
2 conditions required for cracking are…
Heat and a catalyst
600 to 700 degs C
Silica or aluminium oxide catalyst
