Electrolysis Flashcards
What is electrolysis?
The separation of a compound using electricity
Define oxidation and reduction.
Oxidation- Loss of electrons
Reduction- Gain of electrons
What are the electrodes?
Anode- Positively charged
Cathode- Negatively charged
They are the solid conductors in electrolysis.
What needs to be done to Lead Bromide before electrolysis is conducted on it?
It needs to be melted (its insoluble) so the ions are free to move
Which electrode would metals be attracted to?
Cathode (Negative electrode)
Describe the products of the electrolysis of Lead Bromide.
Anode- Bromine atoms discharge (lose electron) pair up and create a gas
Cathode- Lead ions discharge (gain electrons) and lead falls to bottom.
Give the half equations for the electrolysis of Lead Bromide
Pb²* + 2e —> Pb (reduced)
2Br- —> Br²+ 2e (oxidized)
How do we extract metals from metal oxides?
Electrolysis: Reduce the metal (gain electrons)
Metal oxide + Carbon —> ?
Pure metal + Carbon dioxide (reduction)
For metals less reactive than carbon, how are they extracted?
Carbon = more reactive so displaces the metal to form Pure metal + Carbon dioxide
State the order of the reactivity series?
Potassium
Sodium
Calcium
Magnesium
Aluminum
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
How are metal oxides extracted?
Need to be melted using cryolite (lowers MP) e.g Aluminum Oxide to allow ions to move freely. Extracted using Carbon because metal less reactive.
Describe the products of the electrolysis of Aluminum oxide.
Anode- Oxygen (2O²-) loses 4 electrons, lost as gas
Cathode- Aluminium (2Al²*) gains 4 electrons and is collected as pure molten metal.
Give the half equations of the electrolysis of Aluminum Oxide.
Al==> Al^3* + 3e (reduction)
O² + 4e==> 2O^2-(oxidation)
When is electrolysis done with aqueous solutions?
When the compound we are separating is soluble e.g Copper sulfate and Sodium Chloride
Describe the products of electrolysis of Copper sulphate.
Cathode- Copper is discharged as its less reactive than hydrogen.
Anode- Hydroxide is discharged, oxygen and water are the products.
Describe the products of the electrolysis of Sodium Chloride.
Anode- Chloride=> halide is discharged and chlorine gas is released.
Cathode- Hydrogen=> released since less reactive than Sodium.
What are ‘electrolytes’?
Liquid containing ionic compounds
What must be done to ionic compounds before electrolysis?
Melted/aqueous so ions are free to move e.g Lead Bromide melted as insoluble
What is bauxite?
Ore which contains metal oxides.
What does H²O disassociate into?
OH- ions and H+ ions
In aqueous solutions, what will be produced at the anode?
If halide present, then halogen gas produced
If no halide, then OH- ions discharge, producing oxygen gas and water.
In aqueous solutions, what will be produced at the cathode?
If metal more reactive, hydrogen gas released.
If metal less reactive, metal produced.
Give the method for electrolysis in aqueous solutions.
-Set up apparatus + add electrolyte solution
-Add 2 graphite rods+ connect to 12V battery
-Check if metal’s been deposited
-Test for gas
