Chemical changes+ 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)
Br- —> Br+ 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 does electrolysis take place?
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, where the metal is more reactive than carbon, extracted?
Need to be melted using cryolite (lowers MP) e.g Aluminum Oxide to allow ions to move freely.
Describe the products of the electrolysis of Aluminum oxide.
Anode- Oxygen (2O²-) gains 2 electrons, lost as gas
Cathode- Aluminium (Al³*) gains 3 electrons and is collected as pure molten metal.
Give the half equations of the electrolysis of Aluminum Oxide.
Al³* + 3e —> Al (reduction)
2O²- —> O² + 4e (oxidation)
When is electrolysis done with aqueous solutions?
When the compound we are separating is soluble e.g Copper sulfate and Sodium Chloride
