Chapter 11 Redox Reactions And Electrochemistry

Front 1

oxidation

Back 1

loss of electrons

Front 2

reduction

Back 2

gain of electrons

Front 3

oxidizing agent

Back 3

one that becomes reduced
ex) halogens

Front 4

reducing agent

Back 4

one that becomes oxidized
ex) group I/II metals and transition metals

Front 5

oxidation numbers can be known from the periodic table and memorization

Back 5

know

Front 6

balance MnO4- + I- --> I2 + Mn^2+ (pt 1)

Back 6

1. separate into I- --> I2
and MnO4- --> Mn^2+
2. add water to Mn2+ side and add H+ to MnO4- side to be equivalent
3. balance I- --> I2
4. add electrons to respective sides to get = charges
5. multiply charges to get common number and add up the two separate EQs as one

Front 7

final answer to above?

Back 7

10I- + 16H+ +2Mno4- --> 5I2 + 2Mn^2+ + 8H2O

Front 8

electrochemical cells (3)

Back 8

galvanic
electrolytic
concentration

Front 9

which are spontaneous? which are not?

Back 9

spontaneous = concentration/galvanic
nonspontaneous = eletrolytic

Front 10

anode = site of oxidation/reduction
cathode = site of oxidation/reduction

Back 10

anode = oxidation
cathode = reduction

Front 11

movement of electrons is...

Back 11

anode to cathode

Front 12

movement of current is...

Back 12

cathode to anode

Front 13

galvanic cells

Back 13

spontaneous = -/\G
EMF = positive
produces energy = batteries

Front 14

EMF always/never has the opposite sign of the gibbs free energy

Back 14

always

Front 15

draw the set up for a galvanic cell

Back 15

-2 separate beakers
-salt bridge connecting the two
-electrode wire between the two
-anode = Zn + Zn/SO4^2-
-cathode = Cu + Cu/SO4^2-
-anode = predominantly Zn2+
-cathode = predominantly SO4^2-
-salt bridge will push Cl- into anode to counter Zn2+
-salt bridge will push K+ into cathode to counter SO4^2-

Front 16

salt bridges are usually made up of inert electrolytes such as

Back 16

KCl
NH4NO3
NaSO3
KNO3
KI

Front 17

if the two parts of a galvanic cell were not separated, the Cu2+ ions would react with the Zn bar and no work would be obtained

Back 17

know

Front 18

galvanic cells require both a wire and a salt bridge to reach EQ

Back 18

know

Front 19

electrolytic cells

Back 19

non-spontaneous = +/\G
-EMF value
require energy (require outside source)
ex) electrolysis = decompostion

Front 20

draw electrolytic cell

Back 20

has battery
+ end is anode side
- end is the cathode side
-not separated; one container
-no salt bridge
-NaCl in mix; Cl- attracted to anode and Na+ attracted to cathode

Front 21

electrolytic cells are not separated since it is ______

Back 21

non-spontaneous

Front 22

the amount of chemical change induced in an electrolytic cell is directly proportional to the number of moles of electrons that are exchanged during a redox rxn

Back 22

M^n+ + ne- -->M(s)

Front 23

farraday's constant
1F =

Back 23

100,000 Coulombs

Front 24

concentration cells

Back 24

spontaneous = -/\G
+EMF
identical electrodes
-concentration difference pushes rxn forward

Front 25

concentration cells deal with movement of electrons that results in EQ

Back 25

know

Front 26

concentration cells; current ceases when concentrations are =

Back 26

voltage/EMF = 0 at EQ

Front 27

galvanic cells and determing electrode charges

Back 27

since the anode = source of e', it is the negative electrode
the cathode = source of protons, it is the positive electrode

Front 28

movement of electrons in a galvanic cell =

Back 28

negative to positive
-low electric potential to high electric potential

Front 29

electrolytic cell and electrode charge determination

Back 29

the anode is the positive electrode since attached to the positive side of the battery
-the cathode is the negative electrode since attached to the negative side of the battery

Front 30

cathode attracts anions/cations
anode attracts anions/cations

Back 30

cations
anions

Front 31

reduction potentials

Back 31

measured in Volts
-tendency of a species to acquire electrons and become reduced

Front 32

standard reduction potential (Eo)red

Back 32

298K and 1M concentration, 1atm

Front 33

a higher (Eo)red means a greater/lesser tendency for reduction to occur

Back 33

greater

Front 34

a lower (Eo)red means a greater/lesser tendency for reduction to occur

Back 34

lesser
-greater chance to oxidize

Front 35

galvanic species and reduction potential; cathode/anode

Back 35

higher reduction potential = cathode

lower reduction potential = anode

Front 36

electrolytic cell and reduction potential cathode/anode

Back 36

anode = higher reduction potential
cathode = lower reduction potential

REVERSED!!!

Front 37

ex)
Ag+ + e- --> Ag(s) Eo = +.8V
Tl+ + e- --> Tl(s) Eo = -.34V

which is oxidized and reduced?

Back 37

both are in reduced format, the larger (+) value is the reduced one...
the other one is oxidized

Front 38

EMF =

Back 38

cathode - anode

or

reduction + oxidation

Front 39

EMF example
Sm3+ + Rh + 6Cl- --> [RhCl6]3- + Sm

reduction potentials are
-2.41V for Sm3+
+.44V [RhCl6]3-

is it electrolytic or galvanic?

Back 39

Sm3+ is being reduced = -2.41V
while Rh + 6Cl- is being oxidized...
--reverse the .44V --> -.44V and reduction + oxidation = -2.41V + -.44V = -2.85V

electrolytic since EMF = -

Front 40

/\G = -nFEcell

Back 40

n = moles of electrons exchanged
F = 100,000Coulombs
Ecell = EMF of cell

Front 41

/\G is in joules, not kJ

Back 41

!!!

Front 42

coulombs = Joules/Volt

Back 42

!!!

Front 43

Work = q/\V

Back 43

know

Front 44

effect of concentration on EMF

nerst EQ:

Ecell = (Eo)cell - (RT/nF)*(lnQ)

Back 44

Q = [products]/[reactants]

Front 45

concentration does/does not have an effect on the EMF of a cell

Back 45

does
-EMF varies with the changing concentrations of the species involved

Front 46

EMF of a cell can be measured using a ____

Back 46

voltmeter

Front 47

potentiator

Back 47

type of voltmeter that draws no current; can measure difference between two electrodes

Front 48

EMF and Equilibrium constant

EQ:

/\Go = -RTln(Keq)

Back 48

R = 8.3J

Front 49

combining equations...

nF(Eo)cell = RTln(Keq)

Back 49

know this
if Ecell is +, then ln(Keq) is +
--this means K > 1 = products favored

if Cell is (-) than ln(Keq) is (-) and K < 1 = favors reactants

Front 50

Keq > 1 is _____ in forward rxn while a Keq < 1 is not

Back 50

spontaneous

Front 51

if the Keq = 1....then EMF =

Back 51

zero