Unit 2: Alkanes Flashcards
What is a hydrocarbon?
A compound of hydrogen and carbon only.
What is the use of crude oil?
A source of hydrocarbons
Alkanes and cycloalkanes are what kind of hydrocarbon?
Saturated because they have no double bonds.
The effect of chain length on the boiling points of alkanes
As the chain length increases, the boiling point does because the intermolecular forces between molecules get stronger.
There are more points of contact between molecules, leading to more Van Der Waals’ forces eternal molecules.
Effect of branching on boiling points of alkanes
A branched isomer had a lower boiling point than an unbranched isomer.
In a branched alkane, there are fewer points of contact between molecules, leading to fewer van Der Waals’ forces between the molecules.
What is the shape around the Carbon atom in an alkane?
Tetrahedral
Definition of cracking
The breaking down of long-chained saturated hydrocarbons to form a mixture of shorter chained alkanes and alkenes.
What are the dangers of incomplete combustion?
Carbon monoxide. This is produced when a fossil fuel is burned with an insufficient supply of oxygen.
It’s poisonous because it prevents haemoglobin in the red blood cells from binding with oxygen so the body’s tissues become starved of oxygen.
What are short chain alkanes used for?
Fuels
Use in polymer production
Why does the petroleum industry process straight chain hydrocarbons into branched alkanes and cyclic hydrocarbons?
To promote efficient combustion
Conditions for catalytic cracking
zeolite catalyst
450 Celsius
What does increased CO2 levels de combustion of fossil fuels lead to?
Global warming and climate change
Definition of a radical
A species with an unpaired electron
Process of radical substitution
- Covalent bonds are broken by homolytic fission to form radicals with an unpaired electron
- A hydrogen atom in the alkane is substituted by a halogen atom.
Eg. CH4 + Cl2 -> CH3Cl + HCl
Conditions for halogenation of alkanes
Presence of UV radiation
