Flashcards in C1 - Carbon Chemistry Deck (32)
Describe the cracking of liquid paraffin.
1. High temperature and catalyst required.
2. Larger hydrocarbon molecules split up into smaller ones.
3. This makes more petrol (in higher demand).
Why can crude oil be separated through fractional distillation?
The larger the hydrocarbon molecules, the more energy that is required to overcome the intermolecular forces between these molecules. As a result, similar-sized molecules have similar boiling points; this is why they exit the distillation column at the height.
What catalyst is used in cracking?
What two extra products can be produced as a result of incomplete combustion?
Carbon Monoxide and Carbon
What is the word equation for complete combustion?
Hydrocarbon + Oxygen --> Carbon Dioxide + Water
Name three stages in the evolution of the atmosphere.
1. Volcanoes gave out steam and CO2
2. Green plants evolved and produced oxygen.
3. Ozone layer allows evolution of complex animals.
Describe the chemical composition of our atmosphere:
78% Nitrogen, 0.035% Carbon Dioxide, 21% Oxygen
As the earth evolved, how did nitrogen gas begin to fill the atmosphere?
Firstly, ammonia (released from volcanoes) reacted with oxygen to produce nitrogen. Secondly, denitrifying bacteria convert nitrates in the ground to nitrogen gas.
Oxygen put into the atmosphere helped create the ozone layer. Why is the ozone layer important for life on earth?
It blocked harmful rays from the Sun and enabled more complex organisms to evolve.
Describe the carbon cycle.
Carbon dioxide is put into the atmosphere through combustion, respiration and decay. Carbon dioxide is removed from the atmosphere via photosynthesising plants.
How is acid rain caused?
The combustion of fossil fuels with sulfur impurities leads to sulfur dioxide being put into the air. Furthermore, combustion causes oxygen and nitrogen to react - releasing oxides of nitrogen into the air.
When these gases mix with the clouds, they form dilute sulfuric acid and dilute nitric acid. This causes acid rain.
How is photochemical smog caused?
Oxides of Nitrogen combine with oxygen in the air to produce Ozone (O3). Ozone causes breathing difficulties, headaches and tiredness.
What is the balanced symbol equations for catalytic conversion?
2CO + 2NO --> N2 + 2CO2
Why does cooking mean potatoes are easier to digest?
Potato cells are surrounded by a rigid cell wall made up of cellulose. Humans can't digest cellulose, so we cook potatoes to rupture their cell walls. The starch grains in the potato also swell up, making the potato softer and therefore easier to digest.
What is the symbol equation for the thermal decomposition of sodium hydrogencarbonate?
NaHCO3 --> Na2CO3 + CO2 + H2O
How do emulsifiers help oil and water to mix (to make an emulsion)?
The emulsifier has a hydrophilic (likes water, dislikes oil) head and a hydrophobic tail (dislikes water, likes oil). The hydrophilic end bonds to the water molecules and the hydrophobic end bonds to the oil molecules.
What is the word equation for making an ester (perfume)?
Carboxylic acid + Alcohol --> Ester + Water
Name five properties needed by perfumes.
1. Easily evaporates (volatile)
3. Doesn't react with water
4. Doesn't irritate the skin
5. Insoluble in water
What is a solute? What is a solvent?
Solute - substance that is being dissolved
Solvent - liquid it is being dissolved into
Nail varnish doesn't dissolve in water. Why?
1. The attraction between the nail varnish molecules is greater than the attraction between the nail varnish molecules and the water molecules.
2. The attraction between the water molecules is stronger than the attraction between the water molecules and the nail varnish molecules.
How does oil paint dry?
The solvent evaporates and then the oil is oxidised by the oxygen in the air, forming a hard film.
How do emulsion paints dry?
The water-based emulsion dries when the solvent evaporates, leaving behind the binding medium and pigment as a thin solid film.
They dry faster than oil paints.
What determines how 'stretchy' or 'bendy' a polymer will be?
If there are weaker intermolecular forces between the polymer chains, the chains are free to slide over eachother and can therefore be stretched more easily.
On the other hand, if there are strong intermolecular forces, or cross-links between the layers, it is harder for the chains to slide over eachother each other. As a result, the polymer is harder to stretch.
Explain how GORE-TEX is a breathable, yet waterproof material?
1. GORE-TEX is made up of a layer of expanded PTFE that is attached onto another fabric (e.g. nylon) to make it stronger.
2. The PTFE is a micro-porous membrane made up of lots of tiny holes.
3. The pours are big enough to allow water vapour to exit, but too small to allow water droplets to enter.
Hence, breathable and waterproof.
Describe the bonding in an alkane molecule.
Electrons are shared between multiple hydrocarbon atoms in an alkane. This is called covalent bonding.
Why do alkenes decolourise bromine water?
An alkene is an unsaturated compound, meaning it has double bonds available. As a result, an addition polymerisation reaction can occur between the bromine water and the alkene. The result of this reaction is a new colourless solution.
As the size of the hydrocarbon molecule increases, how do its properties change?
1. It's boiling point increases.
2. It gets less flammable.
3. It gets more viscous
4. It gets less volatile
LPG exits at the top of the distillation column. What is LPG made up of?
Mostly propane and butane.
What is produced as a result of cracking large alkane molecules?
- Smaller alkane molecules
- AND, smaller alkene molecules