C3.4 Electrolysis Flashcards
What is electrolysis?
It is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them.
What 3 components are needed for electrolysis to work?
- An electrolyte (a compound in its liquid state or that is aqueous that contains free ions that can conduct electrolysis).
- Two electrolytes (made from metal or graphite) which conduct electricity
- An electrical supply (e.g a battery )
Why can’t covalent compounds act as electrolytes
Because they contain neutral atoms and for electrolysis for work the compounds must contain ions.
What are the two electrodes?
The anode
The cathode
Is the cathode positive or negative?
Negative
Is the anode positive or negative ?
Negative
What are the positive ions called
Cations
What are the negative ions called?
Anions
What happens to the positive ion during electrolysis ?
The positive ions (cations) gain electrons at the cathode and become atoms. Because they gain electrons they are reduced
What happens to the negative ion during electrolysis?
The negative ions (anion) loses electrons at the anode and become atoms. Because they lose electrons they are oxidised
Why are carbon electrodes typically used for electrolysis
Because they have a high melting point and are inert
What happens during the electrolysis of water?
Water is naturally partially ionised. It contains small concentrations of hydrogen ions and hydroxide ions.
During the electrolysis of water:
Hydrogen ions are discharged at the cathode as hydrogen in its gas state
Hydroxide ions are discharged at the anode forming water and oxygen in its gas state
What are the half equations for the electrolysis of water
4H+ (aq) + 4e- —> 2H2 (g). (Reduction)
4OH- (aq) —> 2H20 (L) + O2 (g) + 4e- (Oxidation)
