Chemistry 11th April Flashcards
What is the name for Group 1, Group 7 and Group 8?
Group 1 = Alkali metals
Group 7 = Halogens e.g. Chlorine, Bromine, Iodine
Group 8 = Noble gases
What is the Haber process?
The Haber process is used to manufacture ammonia, which can be used to produce nitrogen-based fertilisers.
nitrogen + hydrogen ammonia
iron catalyst, 200atm pressure, 450’C temperature
Why is the optimum temperature 450’C and optimum pressure 200atm?
The higher the pressure, the greater the rate of reaction and the position of equilibrium shifts further to the right. However the pressure cannot be too high as this would require more expensive equipment and be more dangerous.
The higher the temperature the rate of reaction. But, the temperature cannot be too high because this shifts the position of equilibrium to the left.
What are NPK fertilisers?
NPK fertilisers contain compounds of nitrogen, phosphorus and potassium, and are used improve agricultural productivity
Ammonia can be used to manufacture ammonium salts and nitric acid.
Potassium chloride, potassium sulfate and phosphate rock are obtained by mining.
Phosphate rock is treated with nitric acid or sulfuric acid to produce soluble salts that can be used as fertilisers.
What is the difference between thermosetting polymers and thermosoftening polymers?
Thermosoftening polymers melt when they are heated.
Thermosetting polymers do not melt when they are heated.
Where do we get our hydrocarbons?
Explain the process of fractional distillation of crude oil.
Fractional distillation is used to separate the alkanes according to their size.
The smaller molecules have a lower boiling point so they travel further up the chamber and are distilled higher up. The larger molecules have a lower boiling point so they condense closer to the bottom of the chamber.
Describe the differences between the alkanes distilled at the top versus at the bottom of the chamber.
As you go up the chamber, the alkanes are smaller and are…
Easier to ignite
Flow more easily
Are more volatile (this means they evaporate more easily)
Have a lower boiling point
What is the purpose of cracking?
To produce more useful, smaller chained alkanes, but also to produce alkenes
Long alkane –> Smaller alkane + Alkenes
What are the two types of cracking?
Catalytic cracking
- Uses a catalyst called silica or alumina
- The temperature is 600 to 700 degrees Celsius
Steam cracking
- Mix with steam
- The temperature is 800 degrees Celsius
What is the difference between an alkane and an alkene?
Alkanes and alkenes are both hydrocarbons.
Alkanes have no double bonds, whereas alkenes have at least one double C=C bond.
This means alkanes are saturated whereas alkenes are unsaturated.
What is the chemical test used to distinguish between alkanes and alkenes?
Add bromine water, which is orange brown, to the test liquid.
If the colour of the mixture stays orange brown, it was an alkane - it’s not reacting.
If the colour of the mixture becomes colourless, it was an alkene.
How do alkenes react with halogens?
It is an addition reaction.
Both atoms of the halogen attach - so there’s only one product, the halogenoalkane
Describe the differences between the reacton between alkanes and halogens vs alkenes and halogens
- Alkene + Halogen is a addition reaction
- Alkane + Halogen is a substitution reaction
- Alkene + Halogen does not need UV
- Alkane + Halogen needs UV
- Alkene + Halogen makes DiHalogene (i.e. both halogen atoms join the carbon chain.
- Alkane + Halogen only one halogen atom is attached to the carbon chain.
- Alkene + Halogen there are no extra products
- Alkane + Halogen results in the production of Hydrogen-Halide e.g. Hydrogen Bromide
How do alkanes react with halogens?
Requires the presence of UV light
Substitution reaction: Replacing a H with the Halogen
Product includes Hydrogen-Halogen
