Redox, Rusting, And Iron Flashcards
What is oxidation?
Oxidation is the loss of electrons or loss of hydrogen or gain of oxygen.
What is reduction?
Reduction is the gain of electrons or gain of hydrogen or loss of oxygen.
Oxidation, reduction or redox?
2Mg + O2→ 2MgO
Magnesium gains oxygen and gain of oxygen is oxidation.
or
Magnesium also loses electrons and loss of electrons is oxidation. This is shown by the equation below:
Mg → Mg2+ + 2e-
Is this oxidation, reduction or redox?
CuO + H2 → Cu + H2O
This is reduction as Copper (ll) oxide loses oxygen and loss of oxygen is reduction.
Is this oxidation, reduction or redox?
N2(g) + 3H2(g) → 2NH3(g)
Nitrogen gains hydrogen and gain of hydrogen is reduction.
This one cannot be explained in terms of oxygen (as this is no oxygen in the reaction) and all the substances involved are covalent so there is no loss or gain of electrons.
Usually, oxidation and reduction take place simultaneously in a reaction. We call this type of reaction a redox reaction.
What is rusting?
Rusting is an oxidation reaction. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust.
Here is the word equation for the reaction:
iron + water + oxygen → hydrated iron(III) oxide
Iron and steel rust when they come into contact with water and oxygen – both are needed for rusting to occur.
What are some ways to prevent iron and steel rusting by stopping water or oxygen from reaching the surface of the metal?
There are several ways to prevent iron and steel rusting. Some work because they stop oxygen or water reaching the surface of the metal:
oiling – for example, bicycle chains
greasing – for example, nut and bolts
painting – for example, car body panels
coating with a thin layer of plastic.
What is galvanising?
Galvanising is a method of rust prevention. The iron or steel object is coated in a thin layer of zinc. This stops oxygen and water reaching the metal underneath – but the zinc also acts as a sacrificial metal. Zinc is more reactive than iron, so it oxidises rather than the iron object.
It is sacrificial protection.
What is sacrificial protection?
Magnesium and zinc are often used as
sacrificial metals. They are more reactive than iron and lose their electrons in preference to iron. This prevents iron from losing its electrons and becoming oxidised.
What is the reducing agent in the extraction of iron from haematite and how do you produce it?
Carbon monoxide is the reducing agent which reduces iron (lll) oxide to iron.
The carbon (in coke) burns to form carbon dioxide:
carbon + oxygen → carbon dioxide
C(s) + O2(g) → CO2(g)
Carbon dioxide reacts with more carbon to form carbon monoxide.
carbon dioxide + carbon → carbon monoxide
CO2(g) + C(s) → 2CO(g)
How do you form iron in the blasting furnace?
The equation for the reduction of iron(III) oxide in the blast furnace is:
iron(III) oxide + carbon monoxide → iron + carbon dioxide
Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g)
What is tapped off the bottom after the reduction of iron (lll) oxide?
The molten iron is tapped off the bottom.
What happens after the reduction of iron (lll) oxide?
The calcium carbonate in the limestone thermally decomposes to form calcium oxide.
calcium carbonate → calcium oxide + carbon dioxide
CaCO3(s) → CaO(s) + CO2(g)
What happens after the thermal decomposition of calcium carbonate?
The calcium oxide then reacts with silica (sand) impurities in the haematite, to produce slag – which is calcium silicate.
calcium oxide + silica → calcium silicate
CaO(s) + SiO2(s) → CaSiO3(l)
This reaction is a neutralisation reaction. Calcium oxide is basic (as it is a metal oxide) and silica is acidic (as it is a non-metal oxide). Molten slag is tapped off at the bottom of the blast furnace above the molten iron as molten slag is less dense than molten iron.
