Lesson 1: Industrial Chemistry - Aluminium and Iron

Reactivity Series of Metals

POTASSIUM K

SODIUM Na

CALCIUM Ca

MAGNESIUM Mg

ALUMINIUM Al

(CARBON) <----

ZINC Zn

IRON Fe

LEAD Pb

(HYDROGEN) <----

COPPER Cu

SILVER Ag

GOLD Au

PLATINUM Pt

Metals above carbon must be extracted from their ores by electrolysis.

Metals below carbon can be extracted from their ores using reduction with coke or charcoal.

Metals below hydrogen don't react with water or acid. They don't easily tarnish or corrode.

The reactivity series depends upon 3 standard reactions. These reactions are with:

1. Air
2. Water
3. Dilute Acid

Reaction with AIR

Potassium to Magnesium: Burns very easily with a bright flame.

Aluminium to Copper: React slowly with air when heated.

Silver to Platinum: No reaction

Reaction with WATER

Potassium to Calcium: React with cold water

Magnesium to Zinc: React with steam

Iron: Reacts reversible with steam

Lead to Platinum: No reaction with water or steam

Reaction with Dilute Acid

Potassium to Calcium: Violent reaction with dilute acids

Magnesium to Iron: React fairly well with dilute acids

Lead to Platinum: No reaction with dilute acids

Extracting Aluminium from Bauxite

Bauxite is impure aluminium oxide, Al2O3. It is red-orange.

Because aluminium is high up in the reactivity series, a lot of energy is needed to extract it; this energy comes from ELECTRICITY.

After mining and purifying bauxite, a white powder is left. This is pure aluminium oxide, which melts at over 2000 degrees Celsius.

For electrolysis to work, the oxide needs to be in a molten state. To achieve this, the aluminium oxide is dissolved in molten cryolite. This reduces the temperature to about 900 degrees Celsius, making the process of electrolysis much cheaper and easier.

Extracting Iron in a Blast Furnace

Because iron is below CARBON in the reactivity series, it can be removed from the ore by heating with carbon in a BLAST FURNACE. This is a REDUCTION reaction.

The raw materials in the blast furnace are iron ore (iron oxide), coke (pure carbon) and limestone (calcium carbonate). Coke will reduce the iron oxide. Limestone removes the impurities.

Hot air is blasted into the furnace to accelerate the burning of the coke, causing the temperature to rise to approximately 1500 degrees Celsius.

The main impurity is sand (silicon dioxide).

Slag is used for fertiliser and road building. (Calcium Silicate - CaSiO3)

Properties and uses of Aluminium

Properties:

• Strong, malleable
• Low density
• Resistant to corrision
• Good conductor of heat and electricity
• Can be polished to a highly reflective surface

Uses:

• Low density and strength make it an ideal metal for the construction of aircraft, ladders and lightweight vehicles (alloy called duralumin often used)
• Easily shaped and corrosion-free makes it ideal for drinks cans and roofing material.
• Greenhouses and window frames.
• Heat conduction good for boilers, cookers and cookware.
• Overhead power cables (good conductor, low density)
• Ideal for reflecting surfaces such as mirror, and also heat resistant clothing for fire fighters.

Properties and Uses of Iron

Most iron is used to manufacture steel.

Ore: Type of rock that contains minerals with important elements, including metals.

Electrolysis: A process by which ionic substances are broken down into simpler substances when an electric current is passed through them. It is pretty expensive.

Reduction: A chemical reaction in which oxygen is removed from a compound.