Electrode potentials and electrochemical cells Flashcards
What is the conventional cell representation?
ROOR
Half-cell with most negative potential goes on the left, most oxidised species from each half-cell goes next to the salt bridge.
What is the SHE?
Has a cell potential of 0.00V
Consists of HCl, H2 and uses Pt electrodes
Why is platinum used for electrodes?
Conductor
Inert
What is the formula for Cell emf?
Emf(cell) = E_0 (right) - E_0 (left)
What does the sign of the standard electrode potential say about the species?
More positive = stronger oxidising agent (on left)
More negative = stronger reducing agent (on right)
What effect does increasing concentration have on cell emf?
Makes it more positive as fewer electrons are produced in the reaction
What effect does increasing pressure have on cell emf?
Makes emf more negative as more electrons are produced
What are rechargeable cells?
The reaction that takes place within them is reversible, meaning the reactants can reform
What are the equations for rechargeable lithium ion cells?
Li <-> Li+ + e-
e- + Li+ +CoO2 <-> Li+[CoO2]-
Overall:
Li+ + Li + CoO2 <-> Li+ + Li+[CoO2]-
How can a rechargeable cell be recharged?
The current has to be applied over the cell, which forces electrons to more in the opposite direction, hence causing the reaction to reverse.
What reactions take place in a hydrogen fuel cell?
Anode: H2(g) + O2- -> H2O(g) + 2e-
Cathode: 2e- + 1/2O2(g) -> O2-
Overall: H2(g) + 1/2O2(g) -> H2O(g)
What are the downsides of hydrogen fuel cells?
High flammability of hydrogen and expensive to produce
What is a hydrogen fuel cell?
A fuel cell which uses a continuous supply of oxygen and hydrogen to generate a continuous current. The only by-product is water.
