Electrolysis Flashcards
What will happen if the metal is less reactive than hydrogen
If the metal is less reactive than hydrogen it will form at the cathode
For example copper is less reactive than hydrogen so it will form at the cathode
What will happen if the metal is more reactive than hydrogen
If the metal is more reactive than hydrogen , hydrogen will be released at the cathode
Rules for negative ions at the anode
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What happens if halide ions (group 7 ions ) are present in the electrolyte
If halide ions are present in the electrolyte they will be released at the anode
What happens if there are no halide ions after that
After that ,if there are no halide ions, hydroxide ions will discharge and release oxygen at the anode
What happens after that
After that if there are no halide or hydroxide ions any larger negatively charged ions come next .
Why cant solid ionic compounds conduct electricity
The ions are locked in place by strong electrostatic forces of attraction and are not able to carry charge
Why can electrolysis only occur when ionic compounds are molten or dissolved in an aqueous solution
When ionic compounds are melted or dissolved in water the forces of attraction are broken and the ions are free to move . They can now conduct electricity and carry charge
What are cations
Cations are positively charged ions that are attracted to the negative cathode ( opposites attract
What is reduction and where does it happen
Reduction is gain of electrons and it happens at the negative cathode
What is oxidation and where does it happen
Oxidation is the loss of electrons and it happens at the positive anode that is lacking in electrons
What is the electrode made out of
The elctrode is made out of inert material that wont react with the substances within the electrolyte such as carbon graphite
What happens during the electrolysis of lead bromide (long detailed answer )
- AT THE CATHODE
- The lead ions are attracted towards the negative electrode (the cathode ( opposites attract ))
- The leads ions have a 2+ charge because it is missing two electrons
- at the cathode the lead ion picks up the two electrons its missing and becomes a lead atom
- It is reduced because it gains electrons (OILRIG)
- AT THE ANODE
- Each bromide ion has got a negative charge because it has got an extra electron
- The negatively charged bromide ions are attracted to the positive cathode
- When they get to the cathode they give away their extra electron to become a bromine atom (NOTE : bromine is diatomic)
- The bromide ion has been oxidised because it has lost electrons
What happens during the electrolysis of brine
-AT THE ANODE
-The negatively charged charged chloride and hydroxide ions go to the anode
-The chloride ions are attracted to the anode first ( halide ion ) ( remember rules )
-The chloride ions are then discharged first
- The chloride ions lose one electron each ( oxidation ) Then pair up to become chlorine gas
- The hydoxide ions are left in the solution without being discharged
-AT THE CATHODE
-The positive sodium and hydrogen ions are attracted to the cathode
-The hydrogen is discharged first because sodium is more reactive than it
-Two hydrogen ions each gain an electron (reduction (electrons have been gained ))
-They then pair up and become hydrogen gas
2H + + 2e- -> H2
-The sodium is left behind in the solution
-The sodium and hydroxide ions that have been left behind become sodium hydroxide solution
What are aqueous solutions
Aqueous solutions are solutions where something is dissolved in water
During electrolysis of aqueous solutions what affect do water molecules have on the products of electrolysis
Water molecules split up also forming hydrogen and hydroxide ions
H20 ->H+ + OH-
What ions are there in brine
In brine there are sodium ions,chloride ions and hydrogen and hydroxide ions ( from the splitting up of the water )
What are the products of electrolysis of brine
The products of electrolysis of brine are
- Hydrogen gas
- chlorine gas
- Sodium hydroxide solution
What happens to positivley charged ions
Positively charged ions gain electrons to form a full outer shell (group 1 & 2 ions )
What happens to negatively charged ions
Negatively charged ions lose electrons to gain a full outer shell(group 6 & 7 ions )
What are the properties and uses of aluminium
- Aluminium has a low density and is therefore very light weight.
- This makes it a good material for planes
- Aluminium is also inert because it forms a layer of oxide on its surface which prevents it from reacting with anything
- This makes it a good material to make cans with
How is aluminium extracted
- Aluminium is extracted from its ore ( aluminium oxide )
- It has a very high melting point so is mixed with cryolite to lower its melting point
- This reduces the energy required to electrolyse it which reduces the cost
What happens during the electrolysis of aluminium oxide
First Aluminium is melted ans mixed with cryolite to lower the melting point
- Then the oxide ions are attracted to the positive anode
- The aluminium ions are attracted to the negative cathode
-AT THE ANODE
-oxide ion goes to to the anode and gives up two extra electrons to become an oxygen atom ( O2 molecule ) (2O2 - -> 02 +4e- )
-Oxygen atoms go around in pairs
-AT THE CATHODE
- aluminium picks up three electrons at the cathode and becomes an aluminium atom ( this is reduction , electrons are gained)
Al3+ + 3e- = Al
Why does the positive electrode(anode ) have to be replaced during the electrolysis of aluminium oxide
The anode has to be replaced regularly during the electrolysis of aluminium oxide because the carbon in the carbon graphite reacts with the oxygen in the aluminium oxide to form carbon dioxide . This wears it down over time
Why is extracting by electrolysis so expensive
Melting the compounds takes lots of energy which costs money and lots of energy is also needed to produce the electric current for the electrolysis
What happens during smelting to the copper
During smelting, the copper ore is heated with carbon in a furnace . The copper become copper oxide because of the air inside the furnace . The copper is then displaces by the carbon to make carbon dioxide and crude copper which is still impure
How can you extract copper from its ore
You can either do it by smelting or by using sulfuric acid to make copper sulfate then perform a displacement reaction with scrap iron.
How do you extract copper from its ore by using a displacement reaction with scrap iron and sulphuric acid
- add sulphuric acid to copper ore to get copper sulfate
- Do a reaction between the copper sulfate and the iron
- The iron will displace the copper from the copper sulfate solution , leaving you with iron sulfate and impure copper
What method is used to purify the copper
Electrolysis is used to purify the copper
How is electrolysis used to purify copper
- A lump of impure copper is used as the anode
- pure copper is used as the cathode
- The positively pure copper in the lump of impure copper is attracted to the negative cathode because opposites attract. At the cathode they gain two electrons and become copper atoms again
- The impure copper that isnt attracted to the cathode is left at the bottom of the anode as a sludge
- The pure copper cathode gets bigger because the pure copper from the anode is being attracted there .
- The pure copper at the cathode can then be collected and used in electrical wiring
What happens during electroplating
During electroplating the anode is made out of silver . Any silver atoms in the anode are attracted to a piece of jewellery or cutlery at the cathode because they want to gain their extra electron they lost at the anode . They gain this electron at the cathode and leave a coat of silver atoms on top of the spoon
What will happen in the future to copper extraction
- Copper is a finite resource and in high demand
- The amount available through quarrying is running out
- New ways to extract copper have to be explored
What is phytomining
Phytomining is the extraction of copper using plants
What happens during the process of phtomining
- Plants absorb the copper ions
- You wait until the plants grow so the copper ions become concentrated in the plant
- When the copper ions are concentrated ,the plants are burnt and the copper ions combine with oxygen in the air to form copper oxide which is then left over in the ash
- Then during electrolysis the copper ions become pure copper atoms ( see flashcards before for details 👈) . This can then be used for electrical wiring
What is bio leaching
Bio leaching is using bacteria to extract copper
How does bio leaching work
- When certain bacteria are breaking down material they will absorb copper compounds
- The bacteria will then release these compounds which are called Leachates
- The solution containing the leachates is then electrolysed and the pure copper is extracted
What charge does the anode have
The anode has a POSITIVE charge
What charge does the cathode have
The cathode has a NEGATIVE charge
