Reactivity and Redox Flashcards
Reduction
Gain of Electrons
Or loss of oxygen
Redox Reaction
When oxidation and reductions happen at the same time.
Oxidising Agent
A chemical that accept electrons and gets reduced in a reaction.
Reducing Agent
A chemical that donates electrons and gets oxidised in a reaction.
Displacement Reaction
A reaction where a more reactive metal displaces a less reactive one from its compound.
Reactivity Series
Potassium Sodium Lithium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Hydrogen Copper Silver Gold
Oxidation
Loss of Electrons
Or gain of oxygen
Ore
A naturally-occurring material which contains a metal that can be extracted.
Extraction
Removing a metal from its ore.
Native Metal
A metal found in its metallic form or as an alloy in nature. E.g. Gold
Haematite
- Iron ore
- Fe2O3
- Iron Oxide
Bauxite
- Aluminium Ore
- Al2O3
- Aluminium Oxide
Blast Furnace
Where the extraction of iron from its ore happens.
Rust
- Hydrated Iron Oxide
- Fe2O3
- The product of the corrosion of iron
Corrosion
Deterioration of a metal due to its surroundings, such as air and water.
Sacrificial Protection
Coating a metal (often iron) with a more reactive one. This metal loses its electrons first and stops the metal underneath getting corroded.
Galvanising
Coating a iron in zinc to
1) Work as sacrificial protection
2) Work as a physical barrier
Electrolysis
The break down of an ionic substance that is molten or in a solution by passing electricity through it.
Electrode
In electrolysis, for there to be a circuit, there has to be a:
- Anode - Positive electrode
- Cathode - Negative electrode
Cryolite
Cryolite is a less common ore of aluminium in which aluminium oxide is dissolved in to lower the melting point for electrolysis.
Ionic Half-Equation
These are used to show what is happening at each electrode during electrolysis.
How are the reactions of metals with acid used to deduce the reactivity series?
The faster the reaction happens, the more reactive the metal is. This is the rate at which bubbles are produced and can be tested using a burning splint.
Acid + Metal -> Salt + Hydrogen
How are the reactions of metals with water used to deduce the reactivity series?
- Potassium, Sodium, Lithium, Calcium = Vigourous reaction
- Magnesium, Zinc, Iron, etc. = Not very reactive unless with steam
- Copper = Not at all reactive
How are displacement reactions used to deduce the reactivity series?
A more reactive metal always displaces a less reactive one.
When are redox reactions used in the extraction of metals?
If a metal is less reactive than carbon, heating a metal oxide with carbon monoxide can allow the carbon monoxide reduce the metal oxide by ‘stealing’ the oxygen.
How are metals extracted with regards to the reactivity series?
Above Carbon = Electrolysis
Below Carbon = Heating with Carbon Monoxide
What are the 3 raw materials that are put into the blast furnace?
Iron Ore (Haematite) - Fe2O3
Coke (Carbon) - C
Limestone - CaCO3
What are the main reactions that happen in the blast furnace?
Reducing Iron Ore
C + O2 -> CO2
CO2 + C -> 2CO
3CO + Fe2O3 -> 3CO2 + 2Fe
Removing Impurities
CaCO3 -> CaO + CO2
CaO + SiO2 -> CaSiO3
What are the products of the blast furnace?
- Iron
- Slag
- Waste Gases
What is needed for iron to rust?
Water and Oxygen (Air)
What does each of the raw materials in the blast furnace do?
Iron Ore - Contains iron.
Coke - Contains carbon which is used for reducing iron oxide.
Limestone - Reacts with impurities to form slag.
What are the different methods for preventing rusting?
Barrier - Painting / Coating with plastic - Oiling / Greasing Sacrificial Protection - Galvanising - Coating in more reactive metals than iron
How is aluminium extracted?
1) Aluminium oxide is dissolved in molten cryolite
2) Molten aluminium oxide contains free ions: Al3+ and O2-
3) The positive aluminium ions are attracted to the negative cathode, gain electrons and become aluminium atoms.
4) The negative oxygen ions are attracted to the positive anode, lose electrons there and become oxygen atoms.
Why and what is cryolite used for?
Aluminium oxide is dissolved in cryolite (a less common aluminium ore) before electrolysis due to the fact that it has a lower melting point (950*C), which saves energy.
What is the half-equation for the reaction at the anode, during aluminium extraction?
2O2− → O2 + 4e−
What is the half-equation for the reaction at the cathode, during aluminium extraction?
Al3+ + 3e− → Al
Why does the anode (positive electrode) need to be replaced, during aluminium extraction?
It is made of carbon, which reacts with the oxygen produced there, making CO2, which causes it to get worn away.
Why is aluminium extraction expensive?
- Requires lots of electricity
- Requires energy to melt cryolite
- Positive electrodes need replacing
- Needs to be mined
Uses of Iron
Wrought Iron (Almost pure iron)
- Malleable -> Ornamental gates and railings
Cast Iron (Iron, Carbon, Silicon)
- Hard, but brittle -> Manhole covers and cooking pans
Steel (Iron, Carbon, Some other metals)
- Hard and malleable -> Car bodies and construction girders
Stainless Steel (Iron, Chromium)
- Doesn’t rust -> Cutlery, Cooking pans
Uses of Aluminium
- Doesn’t corrode easily (forms a protective layer) -> Things that come in contact with water e.g. Drinks cans
- Light -> Bicycle frames and aeroplanes
What is the order of the reactivity series?
Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold Platinum
What is a mnemonic for the reactivity series?
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