Reactivity Series: Extraction and Rusting

How do we extract metals placed lower in the reactivity series from ores?

Heat ores with carbon to reduce oxides (ores) to their metals

MO (s) + C (s) → M (s) + CO2 (g)

How do we extract metals placed higher in the reactivity series from ores?

Electrolysis

• Thermal decomposition is more difficult due to thermal stability

• Electrolysis of molten compounds (metal oxide inside) to break the ores down into metals

Where does rusting occur?

Iron and steel (alloy with iron)

What does rusting require the presence of?

Air and water

How can the rate of rusting be increased?

Addition of sodium chloride

What are the implications of the flakiness and brittleness of iron rust?

Rust flakes off and exposes more metal to rust

How does the barrier method prevent rusting?

• Protective layer provides a physical barrier preventing iron from coming into contact with oxygen and water

• E.g. painting, oiling, plastic coating

How does sacrificial protection prevent rusting?

• Sacrificial metals are more reactive than iron

  • Reacts with oxygen and water more readily than iron, corroding in place of iron

  • Preferentially oxidised and loses electrons more easily

• Galvanising

  • Zinc is coated onto a metal surface to act as a protective layer