C6.1 Flashcards
What is an ore?
- A rock or mineral containing enough metal to make it economical to extract the metal
What are 4 ways metals can be extracted from their compounds?
- Reduction
- Electrolysis
- Biological methods
- Displacement reactions
How is iron extracted from its compound?
- Iron ore is heated with carbon in a blast furnace
- Iron (III) oxide is reduced to molten iron
How is aluminium extracted?
- Heating aluminium oxide (Al2O3) until it reaches the liquid state would be very expensive, so it is dissolved in molten cryolite, which reduces its melting point, as it itself has a much lower melting point than aluminium
- It is electrolysed in a cell encased with steel
- Its electrodes are made of graphite
- The sides of the cell are the cathode, and graphite blocks at the top of the cell are the anodes
- Aluminium is produced at the cathode
- Oxygen is produced at the anodes, and reacts with them to produce carbon dioxide, so they need to be replaced frequently
What is bioleaching?
- Bacteria break down metal ores and produce an acidic solution containing metal ions
- This solution is called the leachate
- The leachate can then be processed to produce the metal
What is phytoextraction?
- A crop is planted in soil containing a low-grade ore
- The plants absorb the metal ions through their roots
- They are harvested and burnt
- The ash has a high concentration of metal
- It is processed to produce the metal
Why are bioleaching and phytoextraction used, and what is their disadvantage?
- To extract metal from low-grade ores
- They are cheaper than traditional mining and processing
- They have a much smaller impact on the environment than mining
- Both processes are slow
What is the Contact Process? List its 3 stages.
- Process to make sulfuric acid
- Sulfur burns in the air to make sulfur dioxide:
S + O2 -> SO2 - 2SO2 + O2 -> 2SO3
- H2O + SO3 -> H2SO4
Which stage of the process is reversible? state the conditions chosen for it, and why they’re chosen.
- Stage 2
- A pressure of 2atm, as the position of equilibrium is already far to the right
- A temperature of 450°C as although the forward reaction is exothermic, the rate of reaction needs to be reasonable
- Vanadium (V) oxide catalyst (V2O5)
What is the Haber process?
- N2 + 3H2 -> 2NH3 (reversible)
What are the conditions used in the Haber process, and why were they chosen?
- 200 atm, which is a compromise as a higher pressure should increase the rate of reaction, but high pressures are expensive and dangerous to maintain
- 450°C as although the forward reaction is exothermic, the rate of reaction needs to be reasonable
- Iron catalyst
What else is done to make the production of ammonia efficient?
- Unused hydrogen and nitrogen are recycled
- The gases are cooled so ammonia condenses and leaves the reaction vessel
What are factors to consider when choosing an industrial process?
- Cost of raw materials
- Availability of raw materials
- Energy costs
- Rate
- Equilibrium position
What 3 of the essential elements needed by plants, and what does a lack of them cause?
- Nitrogen
- Phosphorus
- Potassium
- Poor growth and discoloured leaves
- A reduction in the quantity and yield of food
What are fertilisers?
- Substances that replace the elements used by plants
- They can only be used by plants if they’re in a water-soluble form