4.5 - Organics I Flashcards
What is a hydrocarbon?
compounds of hydrogen (H) and carbon (C) only:
What are the fractions of crude oil from top to bottom?
- Refinery gases
- Gasoline
- Kerosene
- Diesel
- Fuel oil
- Bitumen
As you descend through the fractions what happens to the BP?
Low –> High
As you descend through the fractions what happens to the molecular mass?
Low –> High
As you descend through the fractions what happens to the colour?
Light –> Dark
As you descend through the fractions what happens to the viscosity?
Low –> High
Use of refinery gases?
Fuel for home cooking
Use of gasoline?
Fuel for cars
Use of kerosene?
Fuel for aircraft
Use of diesel?
Fuel for trains
Use of fuel oil?
Fuel for ships
Use of bitumen?
Making roads
How is crude oil separated?
Fractional distillation
Where in the fractionating column is hotter?
hotter at the bottom
How does a fractionating column work?
- Heated crude oil vapours enter the column.
- Vapours rise until they reach their boiling point, when they condense.
- Different vapours condense at different heights due to their different boiling points.
- Similar vapours condense together as a fraction.
What are fractions?
Fractions are mixtures containing the hydrocarbons that boil in a particular temperature range.
What are alkanes?
Alkanes are hydrocarbons that fit the general formula CnH2n+2.
What is a displayed formula?
This is a diagram showing the positions of every atom and every bond.
What is a structural formula?
This shows the structure of the molecule in one line, read from left to right like a word.
What is a molecular formula?
This only shows how many carbon and hydrogen atoms there are.
What is a empirical formula?
This only shows the simplest whole-number ratio of carbon to hydrogen.
Properties of a homologous series?
- Similar chemical reactions
- Trends in physical properties (e.g. boiling points, viscosity or colour)
- The same general formula
What is an isomer?
Isomers are molecules with the same molecular formula but different structural formulae.
Complete combustion with alkanes?
This occurs when there is excess oxygen.
It produces only CO2 and H2O:
Alkane + Oxygen → Carbon dioxide + Water
Incomplete combustion with alkanes?
This occurs when there isn’t enough oxygen.
Instead of CO2 this produces a nasty mixture of:
* Carbon monoxide (CO)
* Soot (C) - which causes lung diseases.
It also releases less energy so it makes the alkane less useful as a fuel.
What are the pollutants made in the combustion of alkanes?
- CO2
- NO
- SO2
What are the effects of the pollutants caused by alkane combustion?
CO2 - It is a greenhouse gas that traps heat in the atmosphere and causes climate change.
NO - They dissolve in rainwater to form acid rain
SO2 - It dissolves in rainwater to form acid rain.
What is the reaction between called alkanes and halogens called?
Substitution
What are the conditions needed for the reaction between called alkanes and halogens called?
The reaction requires UV light.
What happens during the reaction between called alkanes and halogens called?
A hydrogen swaps with a halogen
Why do we crack alkanes?
- Shorter molecules are higher in demand because they are more useful.
- Alkenes are needed to make polymers.
What conditions are needed for cracking?
- Temperature: 600 - 700 degrees
- Catalyst: aluminium oxide
Equation for cracking?
Long alkane → Shorter alkane + Alkene
What are alkenes?
Alkenes are hydrocarbons that fit the general formula CnH2n.
What is the structural difference between alkenes and alkanes?
Alkenes have one C=C double-bond, alkanes have a C-C bond.
What are saturated / unsaturated molecules?
Alkenes are referred to as unsaturated because they have a C=C double bond.
By contrast, alkanes are saturated because they don’t have a C=C double bond.
What is the reaction between called alkenes and halogens called?
Addition reaction
What are the conditions needed for the reaction between called alkanes and halogens called?
The reaction happens without UV light - because alkenes are more reactive than alkanes.
What happens during the reaction between called alkenes and halogens called?
All that happens is the C=C breaks and the Br atoms add in where it was.
What colour is bromine water?
Orange
What happens to bromine water when it reacts with alkenes?
Turns colourless
What happens to bromine water when it reacts with alkanes?
Stays orange
How do we form an addition polymer?
An addition polymer forms when molecules with a C=C double bond add into chains.
What are the 4 common polymers?
- Polyethene
- Polypropene
- Polychloroethene
- Polytetrafluoroethene
Uses of polyethene?
- Drinks bottles
- Shopping bags
Uses of polypropene?
- Storage boxes
- Climbing ropes
Uses of polychloroethene?
- Wire insulation
- Drainpipes
Uses of polytetrafluoroethene?
- Non-stick coating
How to dispose of polymers?
- Reuse it.
- Recycle it.
- Incinerate it.
- Chuck it onto landfill.
