P2: 20 Electrode Potentials and Electrochemical Cells Flashcards
What are the features of the conventional representation of cells?
Solids at the ends.
Phase boundaries.
Salt bridge.
R/O//O/R
What are cells used for?
By reference to?
To measure electrode potentials by reference to the standard hydrogen electrode.
What are the standard conditions to measure standard electrode potential?
298 K, 100kPa, 1.00 mol dm^-3
What is an electrode/ half cell?
A metal dipped in a salt solution of its own ions.
How can you calculate the EMF of a cell?
Ecell = ER - EL
What can electrochemical cells be used as?
A commercial source of electrical energy.
What are the electrode reactions in a lithium cell?
Positive electrode:
Li+ + CoO2 + e- -> Li+[CoO2]-
Negative electrode:
Li -> Li+ + e-
What are the three types of cell?
Non-rechargeable, rechargeable, fuel cells
What are fuel cells used for?
To generate an electric current, and don’t need to be electrically recharged.
What are the electrode reactions in an alkaline hydrogen-oxygen fuel cell?
Positive electrode:
O2 + 2H2O + 4e- -> 4OH-
Negative electrode:
2H2 + 4OH- -> 4H2O + 4e-
What are the benefits and risks to using a non-rechargeable cell?
Benefits - cheaper
Risks - generates a lot of waste
What are the benefits and risks to using a rechargeable cell?
Benefits - reusable, last longer, cheaper long-term
Risks - runs out eventually
How is a rechargeable cell recharged?
A current is supplied to force electrons to flow in the opposite direction, reversing the cell reactions.
What are the benefits and risks of using a fuel cell?
Benefits - they convert more of their available energy into kinetic energy, only waste product is water, no CO2 emissions, don’t need to be recharged
Risks - hydrogen and oxygen need to be continuously supplied which needs energy, electricity used to supply hydrogen and oxygen usually comes from burning fossil fuels, hydrogen is highly flammable
