Random questions Flashcards
(10 cards)
Describe how the student can obtain dry crystals of a hydrated solution (5 marks)
- Filter the excess of the solute (metal)
- Heat the solution, so that water evaporates, until crystals start to form.
- Let it cool and crystallise
- Pour excess liquid to obtain crystals
- Leave crystals to dry
Explain why graphite is soft and conducts electricity (5 marks)
- Made of layers with weak forces between them.
- Layers can slide, making it soft
- Each carbon atom makes 3 covalent bonds
- There is one delocalised electron
- Which can carry out an electric current
Explain why hot water evaporates more quickly than cold water.
- Particles have more Kinetic Energy
- This will break the intermolecular forces between water molecules.
Catalyst used in cracking reaction
Alumina / silica
Temperature needed for a cracking reaction
600 to 700 ºC
2 reasons why cracking is important
-Short-chain alkAnes are more useful and more in demand
-AlkEnes are needed to make polymers
Sulfur is an impurity in crude oil
Explain why is this is a problem for the enironment (3 marks)
- Sulfur dioxide is produced when burning impurities in fuels.
- Sulfur dioxide dissolves in water
- Produces acidic rain
How to calculate percentage of oxygen in air
((oxygen volume) / (total volume at start))x 100
Discuss the differences between diamond and graphite (6 marks)
- In diamond, each carbon atom is COVALENTLY bonded to 4 carbon atoms
- In graphite, each carbon atom is COVALENTLY bonded to 3 carbon atoms
- Graphite can conduct electricity
- Graphite has a delocalised electron
- Graphite is soft
- Graphite is made of layers which can slide because layers have weak forces.
Explain why C60 fullerene has a much lower melting point than diamond and graphite (4 marks)
- C60 fullerene has weak intermolecular forces
- Therefore little energy is needed to overcome these forces
- Diamond and graphite, have strong covalent bonds
- Which need a lot of energy to overcome the forces
