Reactions Flashcards
What is displacement
A more reactive metal will displace a less reactive metal from a compound
What affects a displacement reaction
The greater difference in reactivity between the two metals the greater the amount of energy released
What is oxidation
The loss of electrons from a substance . It is also the gain of oxygen by a substance e.g 2mg +O2 = 2mgo oil
What is reduction
The gain of electrons by a substance it is also the loss of oxygen from a substance e.g copper oxide can be reduced to form copper when it reacts with hydrogen. Copper oxide +hydrogen - copper and water rig
What is the oxidising agent
The chemical that causes oxidation
What is the reducing agent
Causes the other chemical to be reduced
What happens with aluminium +iron oxide
= iron + aluminium oxide
The aluminium has been oxidised this means iron oxide is the oxidising agent and iron oxide has been reduced so aluminium is the reducing agent
What is rusting
An oxidation reaction. The iron reacts with water and oxygen to form hydrated iron oxide(rust) . Iron +water +oxygen = hydrated iron oxide
Why does aluminium bot rust
Because it’s surface is protected by a natural layer of aluminium oxide
How canyon prevent rust
Stop oxygen or water reaching the metals surface . Like galvanising - the iron or steep object is coated in a thin layer of zinc that stops oxygen or water reaching the metal underneath , it also acts as a sacrificial metal as it is more reactive than iron so it oxidises in preference to the iron object
What is electrolysis
Electrolysis is the process by which ionic substances are decomposed into simpler substances when an electric current is passed through them
Why does electrolysis only work on ions
Electricity is the flow of electrons , for electrolysis to work the compound must contain ions , covalent compounds don’t work as they contain neutral atoms instead of ions. The ions must also be free to move which is possible when they are dissolved in water or melted
What happens during electrolysis
Positively charged ions move to the cathode they receive electrons and are reduced
Negatively charged ions move to the anode electrode , they lose electrons and are oxidised:
Where are metals and non metals attracted to
Metal is formed At the cathode because it is positive
Non metal element is formed at the anode because it is negative
What is a cathode
Negative electrode
Anode
Positive electrode
What happens in electrolysis in water
If the metal is less reactor than hydrogen metal will be produced t the cathode .if it is more reactive than hydrogen than hydrogen will be produced at the cathode
What happens at the cathode
Reduction
What happens at the anode
Oxidation
Positive charged particle
Anion negative is cation
What are the group 1 metals
They from alkaline solutions when they react with water , this is why they are called the alkali metals
What happens in each reaction with the group 1 metals
Hydrogen gas is given off and the ( metal) hydroxide is produced , the speed and violence of these reactions increased as you go down the group
Why are the group 1 metals reactions similar
All only have one electron in their outer shell
Why does the reactivity do the group 1 metals increase as you go down the group
The atoms get larger as you go down the group
The outer electron gets further from the nucleus as you go down the group
The attraction between the nucleus and outer electron gets weaker as you go down the group
What is the link between the current and time copper is electrolysed for
Copper =current x time
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Hydroxide formula for a group 1 metal t
NaOH
How can copper be purified by electrolysis
If you electrolyse copper sulphate solution using copper electrodes , the anode dissolves into the solution and pure copper is coated onto the cathode
How do you extract aluminium from its ore
Bauxite - purified - alumina (al2o3) - electrolysis - aluminium
How is alumina electrolysed
Molten cryolite is used to dissolve the alumina and layer of carbon acts as the cathode so
At the anode - 60(2-) - 12e = 3o2
At the cathode 4al (3+) + 12 e = 4al
What metals were discovered earlier and why
The lower metals are on the reactivity series , the earlier they were discovered as they were easy to reduce with carbon or were able to be thermally decomposed like lead and copper to then be reduced with carbon : . E.g copper carbonate + heat= CuO + Co2 Metals above carbon in the reactivity series had to be purified using electrolysis which was discovered much later
How is iron made
Iron ore (iron oxide) is put in a blast furnace with alternate layers of coke - coke = carbon burns in air to produce heat, and reacts to form carbon monoxide (needed to reduce the iron oxide) limestone =calcium carbonate -helps to remove acidic impurities from the iron by reacting with them to form molten slag
air - oxygen allows the coke to burn, and so produces heat and carbon monoxide
In the blast furnace, it is so hot that carbon monoxide can be used to reduce the iron oxide in place of carbon:
iron oxide + carbon monoxide → iron + carbon dioxide
Fe2O3 + 3CO → 2Fe + 3CO2
Molten iron then sinks to the bottom of the blast furnace as it is densest and the less dense slags comes out the slag notch
Why do sodium and aluminium have to be purified by electrolysis
Because they are higher than carbon so can’t be displaced by it
What is the reactivity series
Potassium , sodium , lithium , calcium , magnesium , aluminium , carbon , zinc , iron , hydrogen , copper , silver , gold
