chem 116 quiz 8 Flashcards
redox reactions
the process in which electrons transfer from one substance to another
two types of redox chemical reactions
spontaneous and nonspontaneous
the device carrying the redox reactions is called the
electrochemical cell
two types of electrochemical cells and which kind of redox reaction they correspond to
galvanic (aka voltaic) - spontaneous
electrolytic - electrochemical
two kinds of electrodes in electrochemical cells
anode, cathode
anode
where the oxidation reaction occurs; negative (-) label
cathode
where the reduction reaction occurs; positive (+) label
electrons move from the ? to the ? through ? in our case
from the anode to the cathode through the walls of a porous cup
cell potential (Ecell)
the potential difference between the anode and the cathode
cell potential depends on
the tendencies of the redox reaction, the concentrations of the reactants and products in the cell, and the temperature when the reaction occurs
the standard cell potential is
under standard conditions (1.0M concentration for liquid reactants in solution, 1.0atm pressure for gaseous reactions, and 25.0*C)
the standard hydrogen electrode is assigned ? voltage
a zero
the unit of Ecell is
voltage
galvanic cells are used as
batteries
free energy (ΔG) can determine if a reaction is ?
spontaneous or not
ΔG < 0 - spontaneous
ΔG > 0 - nonspontaneous
(opposite of Ecell)
from the Ecell, we can determine the ? of a reaction
spontaneity
Ecell > 0 - spontaneous
Ecell < 0 - nonspontaneous
(opposite of ΔG)
Faraday’s constant (F) is used to
quantify the charge (q) that flows in an electrochemical reaction
**Faraday’s constant F=
96,485C / mol e-
q =
nF
ΔG* =
-nFE*cell or -RTlnk
E*cell =
(RT/nF)lnk where R=8.3145J/molK
ΔG=
ΔG*+RTlnQ where Q is the reaction quotient
Ecell=
E*cell - (RT/nF)lnQ
Nernst equation
Ecell = E*cell - (0.0592C/n)logQ
under standard conditions, Q=1, so Ecell = ?
E*cell as expected
gas law constant
0.0821 Latm/molK
