General Chemistry Ch 12. Electrochemistry

Question 1

Electrochemical cell

Answer 1

Describes any cell in which oxidation-reduction reactions take place

Question 2

Electrodes

Answer 2

Strips of metal or other conductive materials placed in an electrolyte solution, electrons flow from anode to cathode, current flows from cathode to anode

Question 3

Electrolyte

Answer 3

-

Question 4

Anode

Answer 4

Site of oxidation, attracts anions

Question 5

Cathode

Answer 5

Side of reduction, attracts cations

Question 6

Cell diagrams

Answer 6

Shorthand notation that represent the reactions taking place in an electrochemical cell, written from anode to cathode with electrolytes in between, vertical line represents a phase boundary and a double vertical line represents a salt bridge or other physical boundary

Question 7

Galvanic (voltaic cells)

Answer 7

House spontaneous reactions with a positive electromotive force

Question 8

Electrolytic cells

Answer 8

House non spontaneous reactions with a negative electromotive force, these non spontaneous cells can be used to create useful products through electrolysis

Question 9

Concentration cells

Answer 9

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 the two solutions

Question 10

Charge of electrodes galvanic cells

Answer 10

Anode is negatively charged and the cathode is positively charged

Question 11

Charge of electrodes electrolytic cells

Answer 11

Anode is positively charged and the cathode is negatively charged

Question 12

Rechargeable batteries

Answer 12

Electrochemical cells that can experience charging (electrolytic) and discharging (galvanic) states, often ranked by energy density

Question 13

Charging state

Answer 13

Electrolytic state of rechargeable battery

Question 14

Discharging state

Answer 14

Galvanic state of rechargeable battery

Question 15

Energy density

Answer 15

The amount of energy a cell can produce relative to the mass of battery material

Question 16

Lead acid batteries

Answer 16

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, low energy density

Question 17

Nickel cadmium batteries (Ni-Cd)

Answer 17

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 Cd and NIO(OH) electrodes and concentrate the electrolyte, have a higher energy density than lead-acid batteries

Question 18

Nickel-metal hydride (NiMH)

Answer 18

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

Question 19

Surge current

Answer 19

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

Question 20

Reduction potential

Answer 20

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

Question 21

Standard reduction potentials

Answer 21

Ered - Are calculated by comparison to the standard hydrogen electrode under the standard conditions of 298K, 1atm, and 1M

Question 22

Standard hydrogen electrode

Answer 22

SHE - used for comparison for standard reduction potential calculations, has a standard reduction potential of 0V

Question 23

Standard electromotive force

Answer 23

Ecell - The difference in the standard reduction potential between the two half cells

Question 24

Ecell galvanic cells

Answer 24

The difference of the reduction potentials of the two half-reactions is positive

Question 25

Ecell electrolytic cell

Answer 25

The difference of the reduction potentials of the two half reactions is negative

Question 26

Electromotive force and free energy

Answer 26

Always have opposite signs

When Ecell+ –> DELTAG - , case in galvanic cells
When Ecell- –> DELTAG+, case in electrolytic cells
When Ecell = 0 –> DELTAG = 0, case of concentration cells

Question 27

Nernst equation

Answer 27

Describes the relationship between the concentration of species in a solution under nonstandard contains and the electromotive force

Question 28

Equilibrium and standard electromotive force

Answer 28

When Keq > 1, Ecell +
When Keq <1, Ecell -
When Keq=1, Ecell = 0