Redox Flashcards
oxidizing agent gain electron
reduction
reducing agent loss electrons
oxidation
transfer of electrons from one reactant to another
redox reaction
branch of chemistry that deals with the interconversion of electrical energy and chemical energy
electrochemistry
______ are redox reactions
electrochemical processes
energy released by a spontaneous reaction is converted to _____________
electricity
___________ is used to cause a non spontaneous reaction to occur
electrical energy
two kinds of electrochemical cells
- voltaic or galvanic
- electrolytic cell
spontaneous reaction produces electricity
voltaic or galvanic
electrical energy is used to cause a non spontaneous reaction to occur
electrolytic cell
in both cells oxidation and reaction occurs where
oxidation - anode; reduction - cathode
in the short-hand cell notation where is the anode located?
left
needed to complete the electrical circuit
conducting wire and salt bridge
electron flow
conducting wire
cations and anions move from one compartment to another
salt bridge
electron flows from ________ to ________
anode to cathode
how to get the cell potential
anode minus cathode potential
you can’t measure potential on each electrode independently — only differences
true
SHE
standard hydrogen electrode
how do we know which way reaction will go spontaneously?
use electrode potentials, E (potential of electrode versus SHE) to find E° anode and E° cathode, then find E° cell
positive E° cell = spontaneous process
negative E° cell = non spontaneous process
what happens if the E° is more positive
the stronger the oxidizing agent is the oxidized form
what happens if the E° is more negative
the stronger the reducing agent is the reduced form
the standard electrode potential is a __________
relative quantity
the standard electrode potential for a half-reaction refers exclusively to a ______________
reduction reaction
what does the standard electrode potential measures
relative force tending to drive the half-reaction from a state in which the reactants and products are at unit activity
the standard electrode potential for a half-reaction is dependent to what
temperature
limitation of standard electrode potentials
- E° is temperature dependent
- substitution of concentration for activity always introduces error
- formation of complexes, association, dissociation alter E
common standard reducing agent
- iron
- sodium thiosulfate
strong oxidants
- potassium permanganate
- cerium (IV)
widely used for standardization
sodium oxalate
advantage of dichromate
- indefinitely stable
- modest cost
disadvantage of dichromate
- lower electrode potential compared to cerium IV and permanganate ion
a weak oxidizing agent used primarily for the determination of strong reductant
iodine
indicator for iodine titration
starch solution
difference between iodometry and iodimetry
iodometry is for the analyte that is an oxidizing agent added to excess iodide to produce iodine and this iodine is then titrated with sodium thiosulfate while iodimetry is when the analyte is a reducing agent titrated directly with a standard iodine solution
auxiliary reducing reagents
zinc, aluminum, cadmium, lead, nickel, copper, and silver
when an iron containing sample is dissolved it usually contains a mixture of
iron (II) and iron (III) ions
what to do to convert all the iron to iron (II)
treat the sample solution with an auxiliary reducing agent
a reagent is a useful preoxidant or prereductant if it
react quantitatively with the analyte
powerful oxidizing agent
sodium bismuthate
sodium bismuthate is capable of
converting manganese (II) quantitatively to permanganate ion
convenient oxidizing agent, either a solid sodium salt or a dilute solution of the acid
peroxide
