C15 Using our resources Flashcards
What makes one metal more reactive than another?
How easily they form ions - more reactive ones form ions more readily
What is corrosion?
The destruction of materials by chemical reactions with substances in the environment
What is rusting?
The corrosion of iron, both air and water are necessary for iron to rust
What is the word equation for rusting?
iron + water + oxygen –> hydrated iron (III) oxide
Describe how rusting can be prevented
Providing a barrier between iron and any oxygen and water protects the iron from rusting. For example, coating the iron or steel with:
- paint
- oil or grease
- plastic
- a less reactive metal (electroplating)
- a more reactive metal (galvanising)
What is galvanising?
When items are coated with a layer of zinc
What is electroplating?
- This uses electrolysis to place a layer of a less reactive metal over iron
- The solution contains Cu2+ ions which are replaced by the copper cathode
- The copper ions are attracted to the cathode, where they are reduced to form copper atoms and are deposited on the object
- The layer can be made thicker by leaving the equipment running for longer
What is sacrificial protection?
- The covering of iron with zinc
- Zinc is more reactive than metal such as iron, so will oxidise in preference to the iron
- Magnesium can also be used
What is an alloy?
A mixture of a metal and at least one other element
Why are alloys stronger than pure metals?
- The atoms in pure metals are arranged in densely packed layers
- These layers can slide over each other
- When other elements, of different sizes, are added to a pure metal, the layers are distorted
- These layers can no longer slide over each other
What types of alloys are there?
Bronze - an alloy of copper and tin, was commonly used by civilisation before iron extraction methods were developed, it is used today for sculptures, musical instruments
Brass - an alloy of copper and zinc, it does not tarnish and is used for door knobs, buttons and musical instruments
Aluminium alloys - these are lightweight and strong, used in planes and trains
Explain how alloys are used in jewellery
- Gold used in jewellery is usually an alloy as pure gold would be too soft
- Gold is often alloyed with copper, zinc and/or silver
What do the properties of a polymer depend on?
- The monomers used to make it
- The conditions chosen to carry out the reaction
Explain the differences between thermosoftening and thermosetting polymers
- Thermosoftening polymers melt when heated, themsofetting polymers do not melt when they are heated
- Thermosoftening, the polymer chains can move around and over each other, with only weak forces between them, so can be melted easily
- Themosetting, the polymer chains have covalent bond cross links between chains, meaning that they have very high melting points
What are the raw materials for the production of ammonia?
- Nitrogen from the air
- Hydrogen, mainly from natural gas
Explain how the ammonia produced is separated from the unreacted nitrogen and hydrogen in the Haber process
- The mixture of gases is cooled
- So that only the ammonia liquifies
How is the hydrogen for the Haber process formed?
Made by reacting methane gas with steam at very high temperatures:
methane + steam –> hydrogen + carbon monoxide
Explain how the Haber process works
- The purified gases are passed over an iron catalyst at a high temperature (about 450 degrees) and a high pressure (about 200 atmospheres)
- Some of the hydrogen and nitrogen reacts to form ammonia
- The reaction is reversible so some of the ammonia produced breaks down into nitrogen and hydrogen
- On cooling, the ammonia liquifies and is removed
- The remaining nitrogen and hydrogen are recycled to the reactor
What is a polymer?
A long chain of repeating monomers
What are some of the properties of glass?
- Transparent
- Waterproof
- Brittle
- High melting point
- Poor conductor of heat and electricity
How is most glass made?
Heating a mixture of sand, sodium carbonate and limestone
What is borosilicate glass?
- Made from sand and boron trioxide
- Melts at higher temperatures than soda-lime glass
Why is sand a useful component in glass?
Sand is silicon dioxide, which is a giant covalent structure, hence the high melting points
What are ceramics?
Made by shaping wet clay and then heating in a furnace
What are the typical properties of ceramics?
- Hard
- Wear-resistant
- Brittle
- Heat resistant
what are some practical uses of ceramics?
- Pottery
- Bricks
- Dinnerware
- Porcelain
- Tiles
What are composites?
Materials produced from two or more constituent materials that have notably dissimilar chemical or physical properties
Examples of composites
Concrete and fibreglass
What are composites made of?
Most composites are made of two materials, a matrix or a binder surrounding and binding together fibres or fragments of the other materials, which is called reinforcement
What are the two types of glass?
- Soda-lime glass
- Borosilicate glass
What is ammonia used for?
- Used in the manufacture of explosives, plastics, pesticides and textiles
- Its main use is in the production of fertilisers
What process is used to obtain the nitrogen from air?
Fractional distillation
What catalyst is used for the Haber process?
Iron
What conditions are needed for the Haber process?
- The raw materials, nitrogen and hydrogen
- A catalyst, iron
- Temperatures around 450 degrees
- A pressure of around 200 atmospheres
What conditions affect the yield of ammonia?
- concentration
- temperature
- pressure
How is the concentration of ammonia kept low?
Ammonia is continually condensed and removed
How does temperature affect the yield of ammonia?
- A low temperature would give the best yield of ammonia
- Because the forward reaction is exothermic
- So equilibrium will shift right to favour the products and increase the temperature
Why is a low temperature not used in the Haber process?
Although the yield would be best, the rate of reaction would be too slow for the industry
How does pressure affect the yield of ammonia?
- A high pressure would give the best yield of ammonia
- Because there are fewer molecules of ammonia
- So equilibrium will shift to the right to favour the reaction to form ammonia and reduce the pressure
Why is the highest pressure not used?
- Too much energy is needed to increase the pressure
- Stronger equipment would be needed to withstand such high pressure (costly)
How does using a catalyst effect the Haber process?
- The iron catalyst also increases the rate of reaction but it has no effect on the position of equilibrium
- As it increases the rate of the forward and backward reaction equally, it causes equilibrium to be reached faster
Explain the effect of increasing the pressure in the Haber process on the rate of production of ammonia
- An increase in pressure will increase the rate of production of ammonia
- This is because the particles are closer together
- Which leads to more frequent collisions and a faster rate of reaction
Why does ammonia condense but not the other gases?
Ammonia has a higher boiling point
What is a formulation?
A mixture that is designed to produce a useful product
What method is used to obtain soluble salts from a solution?
Crystallisation
What are fertilisers?
- They are added to crops to increase agricultural productivity
- To help crop plants grow so that farmers get a better yield
Why is nitrogen needed in fertilisers?
Needed for cell growth and making proteins in plants
Why is phosphorus used in fertilisers?
Needed to make DNA
Why is potassium needed in fertilisers?
Needed to make enzymes involved in respiration and photosynthesis
What are NPK fertilisers?
- Formulations of various salts containing appropriate percentages of the elements (nitrogen, phosphorus and potassium)
- The salts are water soluble so that they can be absorbed into the soil and taken up easily by plant roots
How is ammonia made into fertilisers?
- Ammonia made in the Haber process can be turned into nitric acid which can be used to neutralise alkalis to make soluble fertilisers
- It can also be used as a solution of ammonia hydroxide and neutralised directly to make ammonium salts
What is the source of phosphorus in NPK fertilisers and how is it obtained?
Phosphate rock is mined, and then treated with acids to form fertilisers, such as ammonium phosphate and calcium phosphate
What is the source of potassium in NPK fertilisers and how is it obtained?
Potassium salts are mined from the ground for uses as fertilisers, such as potassium chloride and potassium sulfate
Why can’t phosphate rock be used directly as a fertiliser?
It is insoluble
What is the compound found in phosphate rock?
Calcium phosphate
Which acid is made when phosphate rock is reacted with nitric acid?
phosphoric acid
compare lab and industrialised production of salts
- Much greater quantities can be made industrially
- Industrial method is continuous rather than batch
- Industrial method is much faster
- Industrial method requires huge quantities of plant machinery
what is produced when phosphate rock is treated with nitric acid?
- phosphate rock is treated with nitric acid to produce phosphoric acid and calcium nitrate
- the phosphoric acid is then neutralised with ammonia to produce ammonia phosphate
what is produced when phosphate rock is treated with sulphuric acid?
- phosphate rock is treated with sulphuric acid to produce single superphosphate
- a mixture of calcium phosphate and calcium sulphate
what is produced when phosphate rock is treated with phosphoric acid?
- phosphate rock is treated with phosphoric acid to produce triple superphosphate
- which is calcium phosphate
