Unit 3c- Electrolysis Flashcards
What is electrolysis?
Using electricity to break down a substance
What happens to an ionic substance when it is melted or dissolved in water?
The ions become free to move around
What is an ionic bond?
Strong electrostatic attraction between oppositely charged ions
What is the name for a substance made of billions of oppositely charged ions joined together?
Giant ionic lattice
Why do sodium ions and chlorine ions form an ionic bond?
There is an electrostatic force of attraction between oppositely charged ions
Define giant ionic lattice
A huge 3D network of ions
State the melting points of ionic substances
High
Explain why ionic substances have high melting points.
Strong bonds between oppositely charged ions are hard to break
Explain why ionic compounds do not conduct electricity when solid
Because the ions are not free to move
Explain why ionic compounds conduct electricity in solution
Because the ions are free to move
Explain why ionic compounds conduct electricity when molten
Because the ions are free to move
What does soluble mean?
Dissolves in water
What does insoluble mean?
Does not dissolve in water
Define oxidation in the context of loss and gain of electrons (Higher only)
Oxidation is the loss of electrons
Define reduction in the context of loss and gain of electrons
(Higher only)
Reduction is the gain of electrons
Which of the substances below has been oxidized and which has been reduced? Al³⁺ + Fe → Fe³⁺ + Al
Aluminium has been reduced and iron has been oxidised
What happens to an ionic substance when it is melted or dissolved in water?
The ions become free to move around
What is the name for the positive electrode?
What is the name for the positive electrode?
What is the name for the negative anode?
The cathode
Do positive ions move to the anode or the cathode?
Cathode- as opposites attract
Do negative ions move to the anode or the cathode?
Anode- as opposites attract
At which electrode would Zn²+(aq) turn into Zn(s)?
Cathode (needs to gain electrons)
At which electrode would Cl⁻(aq) turn into Cl₂(g)?
Anode (needs to lose electrons)
Balance the equation: Al³⁺ + e⁻ → Al
Al³⁺ + 3e⁻ → Al
Balance the equation: Cl⁻ → Cl₂ + e⁻
2Cl⁻ → Cl₂ + 2e⁻
Balance the equation: O²⁻ → O₂ + e⁻
2O²⁻ → O₂ + 4e⁻
In molten electrolysis what are the two products?
The elemental metal and non-metal
What will be the products for the electrolysis of molten iron bromide?
Iron and bromine
What will be the products for the electrolysis of molten zinc oxide?
Zinc and oxygen
For the extraction of which metals is electrolysis needed?
Ones more reactive than carbon, e.g. Group 1,2 and 3
What are the two main disadvantages of using electrolysis to extract metals?
Requires a large amount of energy to melt the compounds and to produce the necessary electricity
Why is aluminium oxide mixed with cryolite when extracting aluminium?
To lower the melting point
What is produced at the anode and cathode in the electrolysis of aluminium oxide?
Aluminium at the cathode and oxygen at the anode
Why does the anode need to be replaced in the electrolysis of aluminium oxide?
The oxygen reacts with the carbon electrode to produce carbon dioxide.
In the electrolysis of sodium chloride solution, what are the products?
Chlorine gas and hydrogen gas
Why is sodium not produced in the electrolysis of sodium chloride solution?
It is more reactive than hydrogen so hydrogen is produced instead.
What is produced at the anode in electrolysis of solutions?
Either a halogen or oxygen (when there is no halogen present)
When is hydrogen produced in aqueous electrolysis?
When the metal is more reactive than carbon (group 1,2 and 3)
When is the metal produced in aqueous electrolysis?
When the metal is less reactive than carbon (transition metal)
When is the group 7 element produced in aqueous electrolysis?
When the salt has a halogen in it
When is oxygen produced in aqueous electrolysis
When the salt does not contain a halogen in it
What is the anode rule for aqueous electrolysis?
If a group 7 element is present it is produced, if not oxygen is produced
What is the cathode rule for aqueous electrolysis?
If the metal is more reactive than hydrogen (Group 1,2 or 3) hydrogen is produced,
If not oxygen is produced
What are the two ions in water?
H+ and OH-
