Electrochemistry Flashcards Preview

A) Chemistry > Electrochemistry > Flashcards

Flashcards in Electrochemistry Deck (41):
0

Electric current

The flow of an electric charge through a substance

1

Electrochemical cell

A device that stages redox reaction that either results in or is driven by an electric current

2

Voltaic cell

An electrochemical cell that produces an electric current from a spontaneous chemical reaction

3

Electrolytic cell

Type of electrochemical cell that consumes current to drive a non-spontaneous chemical reaction

4

Half-cell

The first of two reactions in an electrochemical cell

5

Electrodes

Conductive surfaces through which electrons can either enter or leave the half sells

6

Ampes (A)

Unit of measure for an electric current

1 amp = 1 culoumb

7

Electrical potential difference

The difference in potential energy (joules) per unit of charge

Drives the electric current

8

Volt (v)

Unit of measure for potential difference

9

Electromotive force

The force that moves electrons through a circiut

10

Cell potential (E sub-'cell')

The total voltage between the two cells,
Depends on the relative tendencies of the reactants to undergo oxidation or reduction

11

Standard cell potential

Cell potential for 1M concentration of reactants and products
In a chemical equation

12

Anode

Half-cell in which oxidation occurs

13

Cathode

Half-cell that undergoes reduction

14

Salt-bridge

U-shaped tube that provides the electrolytes to both half-cells in the electrochemical cell

15

Standard electrode potential

The individual potential of the electrode in each half-cell

16

Standard hydrogen electode

The half-cell electrode that is normally chosen to have a potential of zero

17

Predicting current direction

From the anode to the cathode, always

18

Standard electrode potential

The individual potential of the electrode in a half cell

Cell= (.0592/n)*log K

19

Faradays constant

96,485

20

Gibbs free energy

Later used to calculate either temperature, enthalpy(H: energy sum), or entropy(S- number microstates)
ΔG=ΔH-T(ΔS)

21

Nearst equation

(Cell potential-(.0592/n) logQ

22

Dry cell batteries

Electric cell that does not contain high volumes of liquid

23

Electrolysis

The process through which an electric current drives a non-spontaneous reaction

24

Magnetic moment

Magnetic quantity that describes the force that a magnet can exert on electric currents and the torque the magnetic field will exert on it

25

Battery Types

Lead-Acid
Dry-cell (Alkaline and Zinc)
Nickel-Cadium (NiCad)
Nickel-Metal Hydride (NiMH)
Lithium Ion
J

26

Zinc Battery Reaction mechanism

Do not contain high volumes of liquid
Anode Zn(s)→Zn+2(aq)+2e-
Cathode 2MnO2(s)+2NH4+(aq)+2e-→Mn2O3(s)+2NH3(g)+H2O(l)

27

Alkaline Battery reaction mechanism

Slightly different reaction from standard zinc batteries
Anode Zn(s)+2OH-(aq)→Zn(OH)2(s)+2e-
Cathode 2MnO2(s)+2H2O(l)+2e-→Mn2O3(s)+2OH-(aq)

Overall Reaction Zn(s)+2MnO2(s)+2H2O(l)→Zn(OH)2(s)+2MnO(OH)(s)

28

Nickel-Cadmium Battery Reaction mechanism

Anode Cd(s)+2OH-(aq)→Cd(OH)2(s)+2e-
Cathode 2NiO(OH)(s)+2H2O(l)+2e-→2Ni(OH)2(s)+2OH-(aq)

29

Nickel-Metal Hydride Battery reaction mechanism

Anode M,H(s)+OH-(aq)→M,(s)+H2O(l)+e-
Where 'M,' indicates a metal alloy
Cathode NiO(OH)(s)+H2O(l)+e-→Ni(OH)2(s)+OH-(aq)

30

Lithium Ion Battery mechanisms of action

Lithium ions naturally travel from graphite to a (transition metal)-oxide, forming Lithium (transition metal)-oxide and producing a charge
The recharge uses an electric current to strip the lithium ions from the (transition-metal)oxide

31

Hydrogen Fuel cell

Hydrogen gas and a hydroxide solution are supplied to the cell and react, producing water and giving off 4 electrons. These electrons run up the anode, are supplied to the electrical circuit, and re-enter the fuel cell through the cathode where they drive the reaction between oxygen gas and water producing 4OH- ions

32

Alcohol battery reaction mechanism

Ethyl-alcohol (CH3CH2OH) gas reacts with a OH- solution in the anode,producing acetic acid gas (HC2H3O2), liquid water, and giving off 4 electrons which run through the circuit and back to the cathode to drive the reaction between oxygen gas and the water to re-form the OH- solution

33

Electrolysis of water

In an anode:
2H2O(l)→O2(g)+4H(aq)+4e-
Or in a cathode:
2H2O(l)+2e-→H2(g)+2OH-(aq)

34

Gibbs free energy from cell potential

ΔG=-n*F*E.cell

35

Cell potential from Gibbs free energy

E.cell=ΔG/(-n*F)

36

Cell potential from equilibrium constant

E.cell=(0.0592/n)*log(K)

37

Equilibrium constant (K) from the cell potential


log(K)=E.cell/(0.0592/n)

38

Gibbs free energy from equilibrium constant K

ΔG=-R*T*ln(K)

39

Equilibrium constant (K) from Gibbs free energy

Ln(K)=ΔG/(-R*T)

40

Power diffraction

Technique using x-ray, neutron, or electron diffraction on power or microstalline samples for structural characterization of materials