General Chemistry Chapter 12: Electrochemistry Flashcards

1
Q

Electrochemical cell

A

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

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2
Q

Electrodes

A

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

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3
Q

Anode

A

always the site of oxidation. It attracts anions

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4
Q

Cathode

A

always the side of reduction. It attracts cations.

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5
Q

Electrons flow

A

from the anode to the cathode

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6
Q

Current flows

A

from the cathode to the anode

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7
Q

Cell diagrams

A

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

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8
Q

Cell diagrams are written

A

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

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9
Q

A vertical line represents

A

a phase boundary

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10
Q

A double vertical line represents

A

a salt bridge or other physical boundary

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11
Q

Galvanic (voltaic) cells

A

have spontaneous reactions (delta G

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12
Q

Electrolytic cells

A

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

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13
Q

Concentration cells

A

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.

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14
Q

Charge on an electrode for galvanic cells

A

Anode is negatively charged and the cathode is positively charged

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15
Q

Charge on an electrode for electrolytic cells

A

Anode is positively charged and the cathode is negatively charged

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16
Q

Rechargeable batteries

A

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
Q

Lead-acid batteries

A

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
Q

Nickel-cadmium batteries

A

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
Q

Nickel-metal hydride (NiMH)

A

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

20
Q

Surge current

A

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

21
Q

Reduction potential

A

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
Q

Standard reduction potentials (E’red)

A

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

23
Q

Standard electromotive force (Ecell)

A

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

24
Q

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

A
galvanic = positive
electrolytic = negative
25
Q

Relationship between E cell and Delta G

A

always have opposite signs

26
Q

Ecell and Delta G in galvanic cells

A

E = + and G = -

27
Q

Ecell and Delta G in electrolytic cells

A

negative

28
Q

In concentration cells, Ecell and Delta G

A

both = 0

29
Q

Nernst equation

A

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

30
Q

When Keq is greater than 1, Ecell

A

is +

31
Q

When Keq is less than 1, Ecell

A

is -

32
Q

When Keq is equal to 1, Ecell

A

is 0