Unit 5: Electrochemistry Flashcards
What is electrochemistry?
It is the study of the interchange of chemical energy and electrical energy.
What is reduction?
Electron gain
What is oxidation?
Electron loss
What is oxidation state?
The charge the atom would have if all the ve- in the bonds are bonded.
What is an oxidizing agent?
The species that is reduced.
What is the reducing agent?
The species that is oxidized.
What are the steps to predicting redox reactions?
- List all possible reduction and oxidation species.
- Determine the SRA and SOA
- Write out the half reactions
- Balance and combine half reactions
What are the properties of a voltaic cell?
- Chem energy –> electrical energy
- Energy is released from a spontaneous redox reaction
- System does work on surroundings.
What are the properties of an electrolytic cell?
- Electrical energy –> chem energy
- Energy is absorbed to drive a nonspontaneous redox reaction
- Surroundings (power supply) do work on the system (cell).
What half reaction occurs at the cathode?
Reduction
What reaction occurs at the anode?
Oxidation
What are the two ways to create a voltaic cell?
- Mix the chemicals in single compartments
- Chemicals in separate compartments which are connected via a salt bridge
Where do cations flow?
Towards the cathode.
Whare do anions flow?
Towards the anode.
What is cell potential?
The voltage difference between the two half cells.
What is the set up of a cell diagram?
- Anode on the left
- Cathode on the right
- | = phase boundary
- || = salt bridge
- concentrations or pressure are given in ()
- Phase notation is omitted
What happens if Ecell > 0?
- Ec > Ea
- The reaction is spontaneous
What happens if Ecell < 0?
- Ec < Ea
- The reaction in nonspontaneous
What is required for a redox reaction to be successful?
On the redox table the OA needs to be above the RA.
What are the two methods for determining the spontaneity of a redox reaction?
- Write the reactions as reductions and get E from the table.
- Flip reactions to get an overall reaction.
Is E multiplied by an integer?
No because the half cell potential is an intensive property.
What is potential difference (V)?
V= w (work) / q (charge)
What is charge (q)?
q = n (mols of e- transferred) F
Does the work done by a system on the surroundings have a + or - value?
It has a negative value.
wmax = -n F Ecell = G
What happens if G < 0 and Ecell > 0?
The reaction is spontaneous
Does large K correspond to a large positive Ecell?
Yes
What is electrolysis?
When electrical energy drives a nonspontaneous reaction to occur.
What is “overpotential” required for?
It is required to overcome interactions at the surface of the electrode.
If you know the time and the current of a cell you can determine what?
The number of electrons transferred in a redox reaction.
What is an example of electrolysis?
Electrolysis of molten NaCl
At high temperatures, ionic solids melt to form liquids that conduct electricity.
