extraction of metals (iron and aluminium)

questions are taken from pyp

explain how galvanising prevents iron from rusting.

zinc is used to galvanise iron to prevent the iron from rusting is because zinc is more reactive than iron. galvanising will form a protective barrier layer on iron which will prevent water and moisture from reaching its surface. zinc will react more readily with water and oxygen, keeping iron safe from rusting.

name a common ore of iron.

Haematite

define the term alloy

alloys is a mixture of metal with one or few other elements.

what are the essential conditions for the corrosion of iron.

oxygen and water

explain why limestone is used in the blast furnace for the extraction of iron.

limestone is used to remove acidic impurities like silicon dioxide which is also known as sand, it also decomposes to calcium oxide which reacts with silicon dioxide to form slag. slag is known as calcium silicate

thermal decomposition of limestone

CACO3 —> CAO + CO2

formation of slag

CAO+ SIO2 —> CASIO3

why aluminium appears to be unreactive.

it is because aluminium reacts with oxygen to form an oxide layer which is unreactive.

explain why aluminium is used in the manufacture of aircraft.

it has low density

explain why aluminium does not corrode very easily.

this is because aluminium reacts with oxygen to form an oxide layer which is resistant to acids and alkalis and it is impermeable to water or air.

why is aluminium useful for the making of electricity cables. (the properties)

it is because it is a good electrical conductor.

explain why calcium oxide is used in the blast furnace.

the calcium oxide reacts with silicon dioxide to form calcium silicate and then remove silicon dioxide as slag.