2.5 - Hydrocarbons Flashcards
(36 cards)
What is a fossil fuel?
A source of energy that is derived from organisms that lived a long time ago.
What is a non-renewable resource?
Resources that cannot be reformed in a a reasonable time scale.
What is a green house gas?
One that causes an increase in the Earths temperature.
What are 2 advantages to using fossil fuels?
They are available in a variety of forms so that the type of fuel can be matched with its use
They are available at all times (green sources like solar have limited daily availability)
What are the 4 disadvantages of using fossil fuels?
They are non-renewable
Combustion of fuels creates CO2 (a green house gas)
Acid rain forms from sulfur and nitrogen
Carbon monoxide formation which is toxic to haemoglobin as it acts as an inhibitor
What is the equation for alkanes?
CnH2n+2
Are alkanes saturated or unsaturated?
Saturated
What state is a small alkane?
Gas (natural gas like methane)
What state is a large alkane?
Liquids (petrol)
What state is the largest alkane?
Solids (wax)
Why are alkanes generally unreactive?
They are non-polar.
What is complete combustion?
If sufficient oxygen is present, carbon dioxide and water are formed.
What is incomplete combustion?
If insufficient oxygen is present, carbon monoxide and water are formed.
What is halogenation?
The reaction between an organic compound and any halogen.
Basically free radical substitution.
What is the trigger for free radical sub/halogenation?
UV light, will not react in darkness
What is the first stage in free radical substitution?
Initiation
- starts the reaction
- UV light has enough energy to break the cl-cl bond homolytically
- homolytic bond fission occurs when each of the bonded atoms recieves one of the bond electrons so that radicals are formed
- this means they are highly reactive
Cl2 = Cl+Cl
What is the second stage in free radical substitution?
Propagation
- uses radicals as a reactant and then forms a radical as a product
- chain reaction
Cl* + CH4 = CH* + HCl
CH* + cl2 = Ch3Cl + Cl*
What is the final stage in free radical substitution?
The propagation steps continue until 2 radicals meet
Cl* + Ch3* = Ch3Cl
Are alkenes saturated or unsaturated?
Unsaturated as they contain a double bond
What is the formula for an alkene?
CnH2n
How can alkenes be formed in industry?
By cracking petroleum, which is important in polymerisation reactions
What does the double bond create for an alkene?
An area of electron density, called a Pi orbital
A double bond means high reactivity
What is an electrophilic addition reaction?
- as alkenes have a pi bond, they are suseptible to an attack by an electrophile
- the mechanism involves heterolytic bind fission leading to an addition reaction
What is an electrophile?
Any species that can accept a lone PAIR of electrons