5.1 Explain how the methods of extraction if the metals in this section are related to their positions in the reactivity series

The reactive series

Anything LESS reactive than carbon can be displaced from its ore by carbon (e.g.: iron)
Anything MORE reactive than carbon can't and so is extracted by electrolysis (e.g.: aluminium)

5.3 Write ionic half-equations for the reactions at the electrodes in aluminium extraction

These are the two equations you need to know (all thanks go to Hannah Help)

Al³⁺ + 3e^- > Al

• 2O^2- → O₂ + 4e^-

(btw, the Al and the O2 come from the aluminium oxide which is broken down via electrolysis)

5.5 Explain the uses of aluminium and iron, in terms of their properties

Aluminium:
It has low density, which makes it light for its size, and it is strong. This makes it good for the bodies of planes, light vehicles and ladders.
Also, it has a very thin layer of its oxides in its surface, preventing water and oxygen getting to it, and therefore making aluminium a metal which resists oxidation. Aluminium is also malleable (like most metals), making it ideal for drinking cans and cooking foil.
Finally, it conducts heat and electricity well (although not as well as copper, so maybe don't make this your first choice of property) so it is used in power cables and saucepans (and other cooking materials).

Iron:
Iron is one of the three magnetic materials (the other being cobalt and nickel) so it is usually used in electromagnets (for example as a huge electromagnet in scrapyards which picks up cars and other magnetic materials).
There are two types of iron:
- WROUGHT IRON (aka pure iron): malleable and soft, and mainly used as ornamental work in gates)
- CAST IRON: an alloy of iron and carbon (NOT steel). It is very brittle, but has a greater resistance to corrosion than wrought iron or steel and is also VERY STRONG (used for manhole covers on roads and pavements and as engine blocks for petrol/diesel engines)

- Iron can be used to form an alloy called steel which is often used in construction

- Used to make magnets

- Used to make boats, cars, etc.

- Used to make surgical equipment

(more uses click here)

See the BBC Bitesize page - it's really helpful

(http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/rocks/metalsrev2.shtml)

5.4 Describe and explain the main reactions involved in the extraction of iron from iron ore (haematite), using coke, limestone and air in a blast furnace

Figure 1: All the equations you need to know

Figure 2

Coke, which contains carbon, burns in air to produce heat (and CO2), meaning that it is exothermic. The CO2 reacts with MORE C to form carbon monoxide, which is needed to reduce iron oxide.

Limestone, which contains calcium carbonate, is used to get rid of impurities: it reacts with them to produce molten slag, which can be used to build roads.

Hot air is needed so the coke can burn.

Because carbon is higher up in the reactivity series than iron, it displaces iron in the reaction Fe₂O₃ + 3CO  →   2Fe + 3CO₂

In that reaction, iron oxide is reduced to iron and carbon monoxide is oxidised to produce carbon dioxide.

5.2 Describe and explain the extraction of aluminium from PURIFIED aluminium oxide by electrolysis..

..including:
i. the use of molten cryolite as a solvent and to decrease the required operating temperature
ii. the need to replace positive electrodes
iii. the cost of electricity as a major factor

The extraction
1. Bauxite purified into aluminium oxide
2. Dissolved in molten cryolite - this is an aluminium compound and brings down the boiling point (less electricity needed = less energy needed = less cost). Also a solvent for Al2O3
3. At the negative electrode, aluminium is formed.
4. Oxygen forms at the positive electrode
5. Oxygen reacts with the positive graphite anode and it becomes corroded so it needs to be replaced frequently.

The electricity needed in this process costs a lot of money, so the process tries to use as little electricity as possible (which is a lot, to be honest)

Little key notes

• Formula for aluminium oxide: Al2 O3 (numbers in subscript)
• Equation for this is 2Al2 O3 (l) ---> 4Al (l) + 3O2 (g) (numbers in red are used to balance the equation)
• It forms the ions Al 3+ (which is the cathode [-]  ) and O 2- (which is the anode [+])
• Aluminium normally melts at about 2000 degrees C but in cryolite, it melts at about 900 degrees C
• Uses include aircraft construction (it's low density + strong), cans for drinks (easy to shape + corrosion resistant) and boilers and cookers (good heat conductor)
• An ionic compound will only be able to conduct electricity if it is molten or in an aqueous solution.
• Walls of the thingie (see below) are the negative anodes.
• For electricity to flow, there must be either delocalized electrons or ions that are able to move.

Here's a little diagram I drew that looks kind of depressing but hey, I tried.

Figure 1

See key word quizlet - link on the right hand side menu.