Electrode Potentials and Electrochemical Cells Flashcards
Electrochemical Series
List of electrode potentials in numerical order
Half Cell
Container in which oxidation or reduction occurs
Salt-bridge
Allows connection between the 2 half cells and maintains charge balance
Electrode
Can act as either oxidising or reducing agent
Voltmeter
Measures voltage generated by combination of half cells (EMF)
Electrochemical Cells
Combination of 2 half cells
How do electrons flow?
From a more reactive to a less reactive metal
NO PR
Negative-Oxidation(-E°) Positive-Reduction (+E°)
Standard Electrode Potential E°
Voltage measured under standard conditions when the half cell is connected to a Standard Hydrogen Electrode
Standard Conditions against a SHE
1) 1.00mol dm-3 concentration
2) 298K (25°)
3) 100kPa
Standard Cell Potential (E°cell)
E° cell = E° reduced - E° oxidised
Why might EMF values be different?
Non-standard conditions were used
Cell notation
reduced form I oxidise form I I oxidised form I reduced form
Use of Electrochemical Cell
Batteries providing electricity
Lithium Cell
Positive Electrode: Li+ + CoO2 + e- —-> Li+[CoO2]-
Negative Electrode: Li —> Li+ + e-
How are batteries recharged?
Current supplied forces electrons in opposite direction around circuit.
The reaction of Hydrogen being Oxidised at the anode entering the alkaline hydrogen-oxygen fuel cell
2H2(g) + 4OH- (aq) —-> 4H2O (l) + 4e-
The reaction of Oxygen being Reduced at the cathode
O2(g) + 2H2O (l) + 4e- —–> 4OH-
Overall reaction of the H2 and O2 making water
2H2(g) + O2(g) —-> 2H2O (g)
Fuel Cell Advantages
More efficent than internal combustion engines
Do not need to be recharged, only need Oxygen and Hydrogen
Fuel Cell Disadvantages
Hydrogen is highly flammable
Expensive
Fossil fuels are used to pass water through electrolysis
