General Chemistry Chapter 12: Electrochemistry Flashcards Preview

MCAT Gen Chem and O Chem > General Chemistry Chapter 12: Electrochemistry > Flashcards

Flashcards in General Chemistry Chapter 12: Electrochemistry Deck (32)
Loading flashcards...
1

Electrochemical cell

describes 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 the site of oxidation. It attracts anions

4

Cathode

always the side of reduction. It attracts cations.

5

Electrons flow

from the anode to the cathode

6

Current flows

from the cathode to the anode

7

Cell diagrams

are shorthand notation that represent the reactions taking place in an electrochemical cell.

8

Cell diagrams are written

from anode to cathode with electrolytes (the solution) in between.

9

A vertical line represents

a phase boundary

10

A double vertical line represents

a salt bridge or other physical boundary

11

Galvanic (voltaic) cells

have spontaneous reactions (delta G

12

Electrolytic cells

house nonspontaneous reactions (delta G > 0). They can be used to create useful products through electrolysis.

13

Concentration cells

Are a specialized form of a 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 the two solutions.

14

Charge on an electrode for galvanic cells

Anode is negatively charged and the cathode is positively charged

15

Charge on an electrode for electrolytic cells

Anode is positively charged and the cathode is negatively charged

16

Rechargeable batteries

electrochemical cells that can experience charging (electrolytic) and discharging (galvanic) states. Often ranked by energy density - the amount of energy a cell can produce relative to the mass of battery material.

17

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 restonre the original Pb and PbO2 electrodes and concentrate the electrolyte. Have low energy density.

18

Nickel-cadmium batteries

When discharging, consist of a Cd anode and a NiO(OH) cathode in a concentrated KOH solution. When charging, the Ni(OH)2 and Cd(OH)2 plated electrodes are dissociated to restore the original electrodes and concentrate the electrolyte. These cells have a higher energy density than lead-acid batteries.

19

Nickel-metal hydride (NiMH)

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

20

Surge current

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

21

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.

22

Standard reduction potentials (E'red)

calculated by comparison to the standard hydrogen electrode (SHE) under the standard conditions of 298 K, 1 atm pressure and 1 M concentrations

23

Standard electromotive force (Ecell)

the difference in standard reduction potential between the two half-cells.

24

For galvanic cells, the difference of the reduction potentials of the two half reactions = ____
For electrolytic = ___

galvanic = positive
electrolytic = negative

25

Relationship between E cell and Delta G

always have opposite signs

26

Ecell and Delta G in galvanic cells

E = + and G = -

27

Ecell and Delta G in electrolytic cells

negative

28

In concentration cells, Ecell and Delta G

both = 0

29

Nernst equation

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

30

When Keq is greater than 1, Ecell

is +