Chapter 20: Electrochemistry Flashcards
What is an oxidant? (oxidizing agent)
gets reduced so it could oxidize something
Do oxidants gain or lose electrons?
gain
What is a reductant? (reducing agent)
gets oxidized so it could reduce something
Do reductants gain or lose electrons?
lose
What are voltaic cells?
device in which the transfer of electrons between two reactants take place
How do voltaic cells work?
2 reactants not in direct contact (2 separate cells) | redox rxn occurs via flow of e- through electrodes and wires
What is an electrical current?
consists of flowing electrons 9can do electrical work) through a wire and ions moving in solution
What occurs at an anode?
oxidation
What occurs at a cathode?
reduction
What ions in solution migrate toward the anode in a voltaic cell?
anions
What ions in solution migrate toward the cathode in a voltaic cell?
cations
What is potential difference?
difference in potential energy per electrical charge
What is 1 volt equivalent to?
1 Joule/Coulomb
What is cell potential (Ecell)?
potential difference between two electrodes
What is electromotive force (emf)?
its a potential difference that causes the driving force that pushes the electrons through the wire
What is “emf” also called?
the voltage of a cell
What sign must Ecell of a voltaic cell system must have?
(+)
What are standard conditions?
1M, 25ºC, and 1 atm
What 3 things does the magnitude of Ecell depend on?
reactions occuring at cathode and anode | concentrations of the reactions and products | temperature
What is Eºcell?
Ecell under standard conditions
What is the reference half-reaction?
the Eºreduction of 1 atm hydrogen gas
What does SHE stand for?
standard hydrogen electrode
What is standard hydrogen electrode?
the electrode that produces the hydrogen gas reference half reaction | platinum wire
When looking at Eºreduction standard cell potentials, how do you determine which occurs at the cathode or anode?
the more negative the value = more it will be oxidized | the more positive the value = more it will be reduced
What kind of process (spontaneous or not) is a (-)E?
nonspontaneous
What kind of process (spontaneous or not) is a (+)E?
spontaneous
What is the value for Faraday’s constant?
96485 C/mol or J/V•mol
When is the Nernst equation used?
nonstandard conditions (varying concentrations)
What is a concentration cell?
a cell based solely on the emf made from difference in concentration
What is a battery?
portable, self-contained electrochemical power source that consists of one or more voltaic cells
What are primary batteries?
cannot be recharged | throw away when voltage drops to 0
What are secondary batteries?
rechargeable from an external power source when voltage drops
What are the 3 types of SECONDARY batteries?
lead-acid (car) batteries | Nickle-Cadmium/metal hydride batteries | lithium-ion batteries
What is a non-rechargeable battery?
alkaline batteries
What are fuel cells?
voltaic cells that convert chemical energy into electrical energy via conventional fuels (ie: CH4)
What are the 2 reasons as to why fuel cells are not batteries?
not self-contained | fuel must be continually supplied to produce electricity
What is corrosion?
spontaneous redox reactions | metal is attacked by some substance from surroundings = converted into an unwanted compound (ie: rust = iron oxide)
How can you prevent corrosion of iron?
paint over it or cover it with another metal = which will act as a protective layer
What is galvanized iron?
iron covered in zinc = zinc acts as the anode and gets oxidized
What is cathodic protection?
process of preventing corrosion by making the metal into the cathode (as anode gets oxidized = corrosion)
What is a sacrificial anode?
metal oxidized while protecting the cathodic metal
How can nonspontaneous (-)Ecell reactions happen?
only when the driving force is electrical energy (ie battery not flow of electrons
What are electrolysis reactions?
redox rxns driven by an outside source of electrical energy
Where do electrolysis reactions occur?
electrolytic cells
What is an electrolytic cell?
one whole cell (not separate) with 2 electrodes
What is an electron pump?
the voltage source forcing the electrons one specific way
What is the orientation (+)/(-) at the cathode and anode in electrolytic cells?
anode = (+) | cathode = (-) || anode still oxidizes | cathode still reduces
What is the flow of electrons in an electrolytic cell?
anode —-> cathode
