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26 Cards in this Set

  • Front
  • Back
atoms that lose electrosn

OIL rig
atoms that gain electrons

oil RIG
oxidation states
-possible charge values that an atom may hold within a molecule
Oxidation states
Elements: 0
Flourine: -1
Hydrogen: +1
Hydrogen with metal" -1
Oxygen: -2 (except with Hydrogen Peroxide)
Oxidizing agent
what has been reduced
-can be compounds or atoms while what is being oxidized or reduced are only atoms
Reducing agent
what has been oxidized
-can be compounds or atoms while what is being oxidized or reduced are only atoms
if a half reaction has a negative oxidation potential, is it a spontaneous reaction?
NO, half reactions with positive oxidation potentials oxidize spontaneously.
Au3+ (aq) + 3e- --> Au (s) 1.5 potential

What is the oxidizing potential?
Since the equation shows electrons being gained, it is a reduction reaction. The oxidation would be -1.5.

-these are intensive properties and do not change with not multiply by # moles
Balancing Redox Reactions
1) divide into half reactions
2) Balance all elements besides H and O
3)add H20 to one side until O atoms are balanced
4) add H+ to other side until H are balanced
Add e- to one side until charge is balanced
-multiply by integers to equillibriate electrons on both sides
galvanic cell
-converts chemical energy to electrical energy,

-oxidation occurs at the anode, anox
-reduction occurs at the cathode

-anode is negative
-cathode is positive

-two terminals of the galvanic cell must be the same material

-electrons flow from anode to cathode creating a current that flows in the opposite direction

-cell potential for a galvanic cell is always positive

-EMF depends on half reactions, concentrations of reactions and products and temperature
Cell potential in a galvanic cell
-aka electromotive force (emf)
-potential difference between terminals
Salt Bridge in a Galvanic Cell
-liuqid junction that minimizes potential difference created by ions of two different solutions in a cell
-not necessary when electrodes are in contact with same solution
stabdard state of emf of galvanic cell
-found by subtraction potential of reduction hal reaction at the anode from teh potential of the reduction half reaction on the right or cathode

Cathode on right anode on left
Free Energy and chemical energy
Positive cell potential= spontaneous reactoin

ΔG= -nFEmax
n= # moles electrons transferred
F= Faradays constant: 96,486 C/mol
E= voltage

nF=total charge

charge X voltage = work
-non PV work

-ΔG = work done by system
Free energy for non standard conditions
ΔG = ΔGmax + RTln(Q)
Q= reaction quotient

-if we have equillibrium ΔG =0 then plugging that in above
ΔGmax= -RTln(K)

if K=1 ΔG =0
if K >1 ΔG <0
if K <1 ΔG >0

this means if K>1 the reaction is spontaneous at standard state where starting concentrations are exactly 1M
Whe value of all of the following are reversed when a reaction is reversed EXCEPT

1) rate constant
2) enthalpy
3) gibbs energy
4) reaction potential
-rate constant is rarely equal forward and backward..only at equillibrium
Electrolytic cell
-galvanic cells have a positive potential but electrolytic is the only one that can have a negative potential
Concentration Cell
-limited form of a galvanic cell with a reduction half potential taking place in one half while the exact reverse is taking place in other half of cell
-current will flow from more to less concentrated side
-use nernst equation to substitude equations
Electrolytic Cell
- negative potential
-cathode is marked negative and anode is marked positive
an-ox red cat still holds
-hooked to power source
161: Which of the following statements is true concerning the galvanic cell at 25 C?

-Magnesium reduced at cathode
-Concentrations of ions are 1M
-reaction is spontaneous
-reactions in galvanic cells are always spontaneous
Electron flows to cathode or anode in galvanic cell
-reduction takes place at cathode..electrons flow to cathode
Nernst Equation and concentration cell

E= Enaught -.06/n(log(x/y))

If potential is .12 V and a concentration of .1 M Ag+ at anode what is concentration of Ag+ at cathode?
In a concentration cell Enaught = 0 bc the reduction half reaction is equal to reverse of oxidation reaction.

E= -.06/n (logx/y)
.1M at anode =X
n=1 bc 1 e- is transferred
y must be smaller than x bc log of that number has to be negative and therefore that fraction must be less than one.

that fraction needs to equal 10^-2 so y=10
How do you find mass given current, i, time t, F faradays constant?
i= C/s F=C/mole e- transferred
t- s

i/F= moles/s
it/F= moles

then multiply moles by molecular weight
Locations of strongest oxidizing agent and strongest reducing agent
-strongest oxidizing agent is on the upper left while strongest reducing agent is on the bottom right.
Reactions at standard conditions
ΔG =ΔG naught +RTln(Q)
ΔG =ΔG naught
What is the potential E at equillibrium?
At equillibrium, no reaction is favored so there is no potential.