- Fractions have different boiling points
- Boiling point of a molecule depends on chain length
- Cooler at top of column/hotter at bottom of column
- Larger molecules go to bottom of column/smaller molecules go to top of column
Catalytsts, cracking etc.
Nitrogen Oxide (NO) is produced in the engine when a spark/high temperature causes nitrogen and oxygen to react.
N2 + O2 = 2NO
Problems caused by incomplete combustion in a car engine:
- More fuel needed, which costs more
- Have to fit a catalytic converter
Long chain hydrocarbons broken into smaller chain hydrocarbons.
High temperatures are needed to break the C-C bonds
Isomerism, Homologous Series
Homologous series: Organic compounds with the same functional group, but different carbon chain length.
Characteristics of a homologous series:
- Same general formula
- Chemically similar;
- Same functional group
- Trend in physical properties eg inc bp as Mr inc.
- Each member of the series differs from the next by CH2.
Compounds with the same molecular formula, but a different structure.
Branched chain isomers have lower boiling points because...
- They have less surface area
- So less Van der Waals
- Greenhouse gas
- Causes acid rain
- Can be neutralised by CaO
- Causes asthma
- Causes global dimming
- In water in its liquid state, hydrogen bonds are free to break and reform easily as molecules are moving about.
- When water freezes, water molecules are no longer free to move around, and hydrogen bonds hold the molecules in fixed positions.
- In order to fit into this structure, the molecules are slightly less closely packed than in liquid water, meaning ice is less dense - so it floats on the top of ponds!
- This insulates ponds, allowing fish to survive through the winter.
Mp of Al higher than mp of Na because...
- higher nuclear charge
- more delocalised electrons
- stronger electrostatic force of attraction between positive ions and delocalised electrons
Mp of sulfur higher than mp of phosphorus because...
- S is a bigger molecule than P
- so stronger Van der Waals
Bp increase from H2S to H2Te because...
- Atoms get larger
- so increased Van der Waals