ELECTROCHEMISTRY
Redox Reactions
A reaction in which there is a transfer of electrons
There are two simultaneous half-reactions that produce the net
redox reaction
Oxidation (OIL)
A loss of electrons
An increase in oxidation number
Reduction (RIG)
A gain of electrons
A decrease in oxidation number
Oxidising Agent
A substance that is reduced / gains electrons
Reducing Agent
A substance that is oxidised / loses electrons
Anode (ANOX)
The electrode where oxidation takes place
Cathode (REDCAT)
The electrode where reduction takes place
Oxidation Number
The number of charges the atom would have in a molecule if
bonding electrons were transferred completely
Electrolyte
A substance that dissolves in water to give a solution that conducts
electricity
GALVANIC CELLS
A galvanic cell reaction is always spontaneous and exothermic
with two self-sustaining electrode reactions
Chemical energy is converted to electrical energy
Structure
Two half-cells in separate containers
, Anode oxidation ( - electrode)
Cathode reduction ( + electrode)
Anode & Cathode are connected together through an external
circuit current flows from the anode to the cathode
Salt Bridge:
Connects the two half-cells
Filled with a saturated ionic salt(KCl, NaCl, KNO3, Na2SO4)
End of the tubes are closed with a porous material (cotton
wool)
Functions:
1. Complete the circuit (allows current to flow)
2. Maintains the neutrality of the electrolyte solutions
Equilibrium in a Cell
When the circuit is complete, the current will begin to flow
As the reaction proceeds, the rate of the forward reaction will
decrease, therefore the rate of transfer of electrons will also
decrease which results in the Ecellvalue decreasing
The cell potential will continue to decrease gradually until
equilibrium is reached at which point the cell potential = 0
EMF of the Cell
Ecell=Ecathode- Eanode
Ecell=Ereduction-Eoxidation
Ecell=Eoxidising agent-Ereducing agent
Standard Hydrogen Half-Cell
Allocated a reference potential of 0,00 V
All other half-cells will have a potential which is either higher or
lower than this reference
Redox Reactions
A reaction in which there is a transfer of electrons
There are two simultaneous half-reactions that produce the net
redox reaction
Oxidation (OIL)
A loss of electrons
An increase in oxidation number
Reduction (RIG)
A gain of electrons
A decrease in oxidation number
Oxidising Agent
A substance that is reduced / gains electrons
Reducing Agent
A substance that is oxidised / loses electrons
Anode (ANOX)
The electrode where oxidation takes place
Cathode (REDCAT)
The electrode where reduction takes place
Oxidation Number
The number of charges the atom would have in a molecule if
bonding electrons were transferred completely
Electrolyte
A substance that dissolves in water to give a solution that conducts
electricity
GALVANIC CELLS
A galvanic cell reaction is always spontaneous and exothermic
with two self-sustaining electrode reactions
Chemical energy is converted to electrical energy
Structure
Two half-cells in separate containers
, Anode oxidation ( - electrode)
Cathode reduction ( + electrode)
Anode & Cathode are connected together through an external
circuit current flows from the anode to the cathode
Salt Bridge:
Connects the two half-cells
Filled with a saturated ionic salt(KCl, NaCl, KNO3, Na2SO4)
End of the tubes are closed with a porous material (cotton
wool)
Functions:
1. Complete the circuit (allows current to flow)
2. Maintains the neutrality of the electrolyte solutions
Equilibrium in a Cell
When the circuit is complete, the current will begin to flow
As the reaction proceeds, the rate of the forward reaction will
decrease, therefore the rate of transfer of electrons will also
decrease which results in the Ecellvalue decreasing
The cell potential will continue to decrease gradually until
equilibrium is reached at which point the cell potential = 0
EMF of the Cell
Ecell=Ecathode- Eanode
Ecell=Ereduction-Eoxidation
Ecell=Eoxidising agent-Ereducing agent
Standard Hydrogen Half-Cell
Allocated a reference potential of 0,00 V
All other half-cells will have a potential which is either higher or
lower than this reference
