REDOX CELLS Flashcards
1
Q
What is true for both electrochemical and electrolytic cells?
A
- There is a redox reaction and a change of energy between forms.
- Oxidation occurs at the anode
- Reduction occurs at the cathode
- Electrons move through an external circuit
- Ions move through an internal circuit
- Circuit requires an electrolyte between electrodes
- Anions migrate to anode, cations migrate to cathode.
2
Q
How are electrochemical and electrolytic cells different?
A
ELECTROCHEMICAL:
- Spontaneous redox reaction
- Chemical energy to electrical energy
- generates output
- Anode -, cathode +,
- E^0 net pos
ELECTROLYTIC:
- Non-spontaneous redox reaction
- Electrical to chemical energy
- requires input
- Anode +, cathode -,
- E^0 net neg
3
Q
What is the purpose of the electrolyte?
A
- To allow for ion migration
- To complete parts of the circuit
- -> Allows e- to reach ions dissolved a solution to be reduced
4
Q
What are the required properties of an electrolyte?
A
- Must be an aqueous solution of organic compound that conducts electricity
5
Q
What is the purpose of the salt bridge?
A
- To complete the circuit
- To balance charges
6
Q
What are the properties to consider in choosing an electrolyte to fill the salt bridge?
A
- Must be an aqueous ionic solution that allows for ion migration
- Cannot form a precipitate with solution in either cell (otherwise cell will clag up and proper ion migration cannot occur: circuit may not be completed, and increased risk of build up of ions that cannot be further reduced/oxidised around electrodes so cell won’t function properly).
7
Q
What happens if a precipitate forms in the salt bridge?
A
- Salt bridge will clag up: proper ion migration cannot occur, so circuit may not be completed
- Increased risk of build up of ions that cannot be further reduced/oxidised around electrodes
… Thus, cell won’t function properly
8
Q
How does the pH change in the electrolysis of water?
A
- High pH (basic) at cathode ( increase [OH-])
- Low pH (acidic) at anode (increase [H+])
