The rate of a chemical reaction is dependent on the frequency of effective collisions between reactant particles. Heating the reaction mixture increases the average kinetic energy of the reactant particles (Fe₂O₃ and CO). This results in more frequent and more energetic collisions.

However, not all collisions lead to a reaction. A certain amount of energy, known as the activation energy (E_a), must be present for a collision to result in a successful reaction (i.e., the breaking of bonds and formation of new ones).

When the temperature is increased, a greater proportion of the reactant particles possess kinetic energy equal to or greater than the activation energy. This means that a larger fraction of collisions are effective, leading to a higher rate of reaction. Therefore, heating the reaction mixture provides the necessary energy to overcome the activation energy barrier, increasing the frequency of successful collisions and accelerating the reaction.

Cryolite (Na₃AlF₆) plays a vital role in the extraction of aluminium by acting as a solvent for alumina (Al₂O₃). Alumina has a very high melting point, making electrolysis difficult. By dissolving alumina in cryolite, the melting point of the mixture is significantly lowered to around 950-980 °C. This reduction in melting point allows the electrolysis process to occur at a more practical temperature, reducing the energy input required.

Carbon anodes are used in the Hall-Héroult process because they are relatively inert to the molten electrolyte (alumina and cryolite mixture) at the high temperatures involved. They provide a surface for the oxidation of the electrolyte and facilitate the flow of electric current. The primary chemical reaction occurring at the anode is the oxidation of fluoride ions:

The carbon anodes need to be replaced regularly because they are gradually consumed during the electrolysis process. Specifically, the fluoride ions (F^-) in the electrolyte are oxidized to fluorine gas (F₂) on the anode surface. This reaction causes the carbon anodes to erode and be consumed over time. Therefore, regular replacement is essential to maintain the efficiency of the electrolysis process and prevent the build-up of impurities.

The reduction of iron(III) oxide (Fe₂O₃) by carbon monoxide (CO) is a key step in the extraction of iron. The reaction can be represented by the following equation:

Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g)

This reaction occurs at high temperatures, typically around 2000°C, within the blast furnace. The high temperature is necessary to provide the activation energy required for the reaction to proceed. The presence of carbon monoxide is crucial as it acts as the reducing agent, donating electrons to the iron(III) oxide and causing it to be reduced to iron. The carbon monoxide is produced from the partial combustion of coke within the furnace. The reaction is exothermic, meaning it releases heat, which further contributes to maintaining the high temperature within the blast furnace and driving the reaction forward.