Alkanes and alkenes Flashcards
1
Q
What type of compounds are alkanes and alkenes?
A
- Covalent compounds
- bond formed btwn non-metals
2
Q
Physical properties of alkanes and alkenes
A
- Low MP/BP
- Insoluble in water
- Soluble in organic solvents
- Do not conduct electricity in any state
3
Q
How physical properties change going down the series
A
- MP/BP increase
- larger molecular size
- stronger intermolecular forces - More viscous
- Densities increase
- Flammability decreases
4
Q
How physical properties change going down the series
A
- MP/BP increase
- larger molecular size
- stronger intermolecular forces - More viscous
- Densities increase
- Flammability decreases
5
Q
Why alkenes burn with smokier flame
A
- Alkenes have higher percentage of carbon
- Need more O2 for complete combustion
- Higher chance of incomplete combustion, more carbon left as soot, smokier flame
6
Q
Chemical Properties of Alkanes
A
- Generally unreactive
- Combustion
- Substitution rxn
7
Q
Why are alkanes generally unreactive
A
- consists of only C-C bonds (Single), C-H bonds
- bonds are strong, difficult to overcome
8
Q
Combustion (Alkanes)
A
- ignited by spark/flame
- burn readily in xs air
- produce CO2 and water vapour
- highly exothermic
- alkanes –> gd fuels
9
Q
Substitution rxns
A
- alkanes react with halogens
- e.g. chlorine, bromine
- presence of UV light
- methane + chlorine –> chloromethane + hydrogen chloride
10
Q
Cracking
A
- breaking down of long-chain hydrocarbons
- into smaller molecules
11
Q
Products of cracking
A
- Small alkanes
- Small alkenes
- Hydrogen gas
11
Q
Products of cracking
A
- Small alkanes
- Small alkenes
- Hydrogen gas
12
Q
2 ways of cracking
A
- Big alkane –> small alkane + small alkene
2. Big alkane –> small alkene + H2
13
Q
Uses of cracking
A
- Produce smaller chain of alkenes (starting materials for alcohols, plastics)
- Produce H2 needed for fertilisers
- Produce petrol frm lubricating oil and diesel, more useful, higher demand
14
Q
Evidence of cracking
A
- bubbles of gas/effervescence
- shows liquid pertoleum (higher bp) converted into smaller alkanes and alkenes (lower bp)
