Ch 12: Electrochemistry Flashcards Preview

General Chemistry > Ch 12: Electrochemistry > Flashcards

Flashcards in Ch 12: Electrochemistry Deck (32):
1

electrochemical cell

any cell in which oxidation-reduction reactions take place. Certain characteristics are shared between all types of electrochemical cells

2

Electrodes

strips of metal or other conductive materials placed in an electrolyte solution

3

anode

always site of oxidation. it attracts anions

4

cathode

always the site of reduction. it attracts cations

5

electrons flow from ____ to ____

anodes
cathodes

6

current flows from ____ to ____

cathode
anode

7

cell diagrams

shorthand notation that represents the reactions taking place in an electrochemical cell

8

cell diagrams are written from anode to cathode with ____ in between

electrolytes (the solution)

9

a vertical line represents a ____, and a double vertical line represents a ____ or other physical boundary

phase boundary
salt bridge

10

galvanic (voltaic) cells

house spontaneous reactions (delta G

11

electrolytic cells

house nonspontaneous reactions (delta G > 0) with a negative electromotive force. these nonspontaneous cells can be used to create useful products through electrolysis

12

concentration cells

specialized form of galvanic cell in which both electrodes are made of the same material. rather than a potential difference causing the movement of charge, it is the concentration gradient between two solutions

13

charge of an electrode is dependent on

type of electrochemical cell one is studying

for galvanic cells, anode is neg and cathode is pos
for electrolytic cells, anode is pos and cathode is neg

14

rechargeable batteries

electrochemical cells that experience charging (electrolytic) and discharging (galvanic) states

often ranked by energy density, the amount of energy a cell produces relative to the mass of battery material

15

lead-acid batteries

when discharging consist of a Pb anode and a PbO2 cathode in a concentrated sulfuric acid solution.

When charging, the PbSO4 plated electrodes are dissociated to restore the original Pb and PbO2 electrodes and concentrate the electrolyte. these cells have low energy density

16

nickel-cadmium batteries (Ni-Cd)

when discharging consist of a Cd anode and a NiO(OH) cathode in a concentrated KOH solution

when charging, Ni(OH)2- and Cd(OH)2- plated electrodes are dissociated to restore the original Cd and NiO(OH) electrodes and concentrate the electrolyte. these cells have a higher energy density than lead-acid batteries

17

nickel-metal hydride (NiMH)

batteries have more or less replaced Ni-Cd batteries because they have higher energy density, are more cost effective, and are significantly less toxic

18

surge current

above-average current transiently released at the beginning of the discharge phase; it wanes rapidly until a stable current is achieved

19

reduction potential

quantifies the tendency for a species to gain electrons and be reduced. the higher the reduction potential, the more a given species wants to be reduced.

20

standard reduction potentials (Enot,red) are calculated by comparison to the ____ under standard conditions ____

standard hydrogen electrode (SHE)

298K, 1 atm pressure, 1 M concentrations

21

standard hydrogen electrode has a standard reduction potential of

0V

22

Standard electromotive force (Eknot, cell)

difference in standard reduction potential between the two half-cells

23

for galvanic cells, the difference of the reduction potentials of the two half-reactions is ____; for electrolytic cells, the difference of the reduction potentials of the _____ is negative

positive

two half-reactions

24

electromotive force and ____ always have opposite signs

change in free energy

25

when Eknot,cell is positive, delta G is

negative. This is a galvanic cell

26

When Eknot,cell is negative, delta G is

positive. This is the case in a electrolytic cell

27

When Eknot,cell is 0, delta Gknot is

0 this is case in concentration cells

28

nernst equation

describes the relationship between the concentration of a species in a solution under nonstandard conditions and the electromotive force

29

there is a relationship between Keq (equilibrium constant) and

Eknot,cell

30

When Keq (ratio of products conc at equilibrium / reactants all raised to their stoichiometric coefficients) > 1

Ecell is positive

31

Keq

negative

32

When Keq = 1 then Ecell is

0