Electrolysis Flashcards
(38 cards)
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
