Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > electrode potentials > Flashcards

electrode potentials Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

what is the process of oxidation and reduction expressed in terms of

A

electron transfer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

oxidation

A

loss of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

reduction

A

gain of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

oxidation is an increase in

A

oxidation state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

reduction is a decrease in

A

oxidation state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what can we work out by assigning oxidation states

A

which species have been oxidised and which have been reduced without writing half equations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

oxidising agent

A

species that accepts electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

reducing agent

A

species that donates electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

example of an oxidising agent

A

halogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

example of a reducing agent

A

reactive metals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does an electrochemical cell use the electron transfer which occurs during a redox reaction to do

A

produce electrochemical energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what does each electrochemical cell consist of

A

2 half cells corresponding to the two half equations occurring in the redox reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does a half cell consist of

A

two species of the same element in different oxidation states

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the electrode in a copper half cell

A

solid copper

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the solution in copper half cell

A

1 mol dm3 copper 2+ ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the IUPAC convention for writing half equations for electrode reactions

A

to give them as an equilibrium reaction where the forward reaction is reduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what must the half cells be connected via in order to make use of the electrical energy produced in a redox reaction

A

connected via an external circuit and a salt bridge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the circuit usually

A

a conducting wire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what flow through the wire

A

electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does the salt bridge consst of

A

a strip of filter paper soaked in saturated potassium nitrate or potassium chloride solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what flows through the salt bridge

A

ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are the electrodes connected to

A

a high resistance voltmeter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what does the voltmeter easure

A

electromotive force (emf) in volts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is the emf

A

potential difference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is the other name for emf

A

cell potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what are the standard conditions are there for a half cell

A
  • 100kPa
  • 298K
  • solution of ions at 1moldm-3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

which metal goes on the rhs

A

the more positive metal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

which metal goes on the rhs in the standard copper-zinc cell

A

copper

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

why is the copper the positive electrode in the copper-zinc cell

A

because it is connected to the positive terminal of the voltmeter and so is the positive electrode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is the IUPAC convention for cell diagrams

A

to draw the positive electrode as the half cell on the RHS (except when measuring standard electrode potential against hydrogen electrode when hydrogen always on left)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what occurs at the negative electrode

A

oxidation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what occurs at the positive electrode

A

reduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

where do electrons flow in cell

A

from negative electrode to positive electrode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what does the standard electrode potential of a half cell indicate

A

its tendency to lose/gain electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

is it possible to measure the standard electrode potential of one half cell alone

A

no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is used as a reference to measure standard electrode potential against

A

a primary standard

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

`what is the primary standard for measuring electrode potentials

A

the standard hydrogen electrode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what emf does the standard hydrogen electrode have by definition

A

0.00V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

standard hydrogen electrode

A
  • H2 gas at 1 00kPa
  • 1 moldm-3H+ (aq)
  • 298K
  • Pt electrode
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

equation for standard hydrogen electrode

A

2H+ + 2e->< H2(g)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

standard electrode potential

A

emf of a half cell compared with a standard hydrogen half-cell

measured at 298K, all solutions having conc of 1moldm-3 and all gases at a pressure of 100kPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what is the standard electrode potential found by measuring

A

the voltage of a cell with the standard hydrogen half cell as one half cell and the half cell under investigation as the other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what gives the sign of the electrode potential

A

the polarity of the half cell relative to the hydrogen half cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

conventional representation of a cell: what does a vertical solid line indicate

A

a phase boundary eg between a solid and a solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

conventional representation of a cell: what does a double vertical line show

A

a salt bridge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

conventional representation of a cell: which species for each half cell is written next to the salt bridge

A

the species with the highest oxidation state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

conventional representation of a cell: where is the standard hydrogen half cell shown when measuring the standard electrode potential of a half cell

A

LHS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

conventional representation of a cell: where is the positive electrode shown when showing any other electrochemical cell

A

RHS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

conventional representation of a cell: where is the negative electrode shown when showing any other electrochemical cell

A

LHS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

what is an ion/ion half cell

A

half cells in which both species are aqueous ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

what must an ion/ion half cell contain

A

both the oxidised and reduced species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what electrode is used in an ion/ion half cell

A

platinum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what are standard electrode potential values determined by

A

measurement against the standard hydrogen electrode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what are all reactions shown as in the electrochemical series

A

reductions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

what can we determine looking at the electrochemical series

A

the relative reactivity of different species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

metals react by losing what to form positive ions

A

electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

what do reactive metals undergo more readily

A

oxidation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

the most reactive metals will have the most negative

A

E0 values

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

what are the most reactive metals good at

A

being reducing agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

what is the correlation between negativity of E0 value of metal and tendency for species on RHS to lose electrons and be oxidised

A

more negative E0 value, greater tendency for species on RHS to lose electrons and be oxidised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

how to non metals react

A

by gaining electrons to form negative ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

reactive metals undergo what more readily

A

reduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

most reactive non metals will have most positive what

A

E0 values

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

most reactive non metals are good at what

A

being oxidising agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

correlation between positivity of E0 value of non metal and tendency for species of LHS to gain electrons and be reduced

A

more positive E0 value, greater tendency for species on LHS to gain electrons and be reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

what must a half cell be connected to to determine the electrode potential of it

A

the standard hydrogen electrode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

what can be connected to generate an emf

A

any 2 half cells

68
Q

what is the cell potential the difference between

A

the standard electrode potentials of the two half cells

69
Q

what is chemical energy converted into in an electrochemical cell

A

electrical energy

70
Q

what does the emf drop to once the chemicals are used up

A

0.00v

71
Q

which half equation goes forwards

A

the one with the more positive e0 value- gains electrons

72
Q

which half equation goes backwards

A

the one with the more negative e0 value- loses electrons

73
Q

how to determine which reaction will occur in the cell or in a test tube

A

add the two half equations, making sure that the number of electrons lost equals number of electrons gained

74
Q

measuring electrode potential for a metal/metal ion half cell eg copper: equation

A

Cu2+ +2e- <> Cu(s)

75
Q

the conventional representation of a cell: what does a vertical solid line indicate

A

a phase boundary eg between a solid and a solution

76
Q

the conventional representation of a cell: a double vertical line shows the

A

salt briddge

77
Q

the conventional representation of a cell: the species with the highest ? for each half cell is written next to the salt bridge

A

oxidation state

78
Q

the conventional representation of a cell: when measuring the standard electrode potential of a half cell the standard hydrogen half cell is always shown on the

A

left hand side

79
Q

The conventional representation of a cell: on which side is the positive electrode shown

A

The RHS

80
Q

The conventional representation of a cell: on which side is the negative electrode

A

Left hand side

81
Q

The conventional representation of a cell: using what equation can the cell potential be calculated

A

E0RHS-E0LHS

82
Q

To measure E0 for ion/ion half cells: what are ion/ion half cells

A

Half cells in which both species are aqueous ions

83
Q

To measure E0 for ion/ion half cells: what must the half cells contain

A

Both the oxidised and reduced species

84
Q

To measure E0 for ion/ion half cells: what electrode is used

A

Platinum

85
Q

The electrochemical series: in what order can the standard electrode potential values determined by measurement against standard hydrogen electrode be placed in

A

Numerical order

86
Q

The electrochemical series: what are all reactions shown as

A

Reductions

87
Q

The electrochemical series: what can we determine by looking at electrochemical series

A

Relative reactivity of different species

88
Q

The electrochemical series: metals react by losing _____ to form ______ ions

A

Losing electrons to form positive ions

89
Q

The electrochemical series: reactive metals undergo what more readily

A

Oxidation

90
Q

The electrochemical series: the most reactive metals will have the most _______ E0 values

A

Negative

91
Q

The electrochemical series: the most reactive metals are good _______ agents

A

Reducing

92
Q

The electrochemical series: the more negative the E0 values the ________ the tendency for the species on the _____ to _____ electrons and be _______

A

The more negative the E0 the greater the tendency for the species on the RHS to lose electrons and he oxidised

93
Q

The electrochemical series: non metals react by ______ electrons to form ______ ions

A

Gaining electrons to form negative ions

94
Q

The electrochemical series: reactive non metals undergo ______ more readily

A

Reduction

95
Q

The electrochemical series: the most reactive non metals will have the most _____ E0 values

A

Positive

96
Q

The electrochemical series: the most reactive non metals are good ______ agents

A

Oxidising

97
Q

The electrochemical series: the more positive the E0 the _______ the tendency for the species on the _____ to _____ electrons and be _____

A

The more positive the E0 the greater the tendency for the species on the LHS to gain electrons and be reduced

98
Q

Measuring the emf of an electrochemical cell, required prac: how else can emf be determined other than using hydrogen electrode

A

Any two half cells can be connected to generate an emf

Cell potential = difference between standard electrode potentials of 2 half cells

99
Q

Using electrode potentials to predict chemical reactions: what is chemical energy converted to in an electrochemical cell

A

Electrical energy

100
Q

Using electrode potentials to predict chemical reactions: when did the emf drop to 0.00V in an electrochemical cell

A

Once the chemicals are used up

101
Q

Using electrode potentials to predict chemical reactions: how can we predict what reaction occurs

A

By looking at the E0 values of the two half cells

102
Q

Using electrode potentials to predict chemical reactions: which half equation gains electrons and what does this mean

A

The half equation with the more positive E0 value gains electrons, so goes forwards

103
Q

Using electrode potentials to predict chemical reactions: which half equation loses electrons and what does this mean

A

The half equation with the more negative E0 value loses electrons, so goes backwards

104
Q

Using electrode potentials to predict chemical reactions: what must be certified when adding the two half equations together

A

Number of electrons lost=number of electrons gained

105
Q

Change in mass of the electrode: why does the mass of the negative electrode decrease when a current is drawn

A

The metal will be oxidised to metal ions

106
Q

Change in mass of the electrode: what happens to the mass of the positive electrode and why

A

Increases as metal ions turn to metal

107
Q

The effect of concentration on the emf of a cell: what are the values of E0 measured under standard conditions of

A

100kPa, 298K, 1 mol dm-3

108
Q

The effect of concentration on the emf of a cell: what can be used to predict how concentration changes affect EMF

A

Le chateliers lrinciple

109
Q

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Cu2+]>1moldm3

A
  • equilibrium shifts right
  • ECu more negative
  • Cu2+ gains more electrons
  • Ecell will increase- bigger difference in E
110
Q

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Cu2+]<1moldm-3

A
  • equilibrium shift LHS
  • ECu less positive
  • Cu2+ will gain feevwr electrons
  • Ecell will decrease- cell has smaller difference in E
111
Q

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Zn2+]>1mol dm-3

A
  • equilibrium will shift RHS
  • EZn less negative
  • Zn will release fewer electrons
  • Ecell will decrease as cell has smaller difference in E
112
Q

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Zn2+] < 1moldm-3

A
  • equilibrium shift LHS
  • EZn become more negative
  • Zn will release more electrons
  • Ecell will increase as cell has a bigger difference in E
113
Q

if conditions are no longer standard what is cell potential written as as opposed to E0Cell

A

ECell

114
Q

Limitations of using electrode potentials tocpredict redox reactions

A
  • predictions using electrode potentials tell us about equilibrium but not RoR
  • many reactions in laboratory not done under standard conditions- will affect electrode potential vales
115
Q

Commercial applications of electrochemical cells: what 3 main types can cells be divided into

A
  • non- rechargeable cells
  • rechargeable cells
  • fuel cells
116
Q

Non rechargeable cells: how are they designed to be used only once

A

Reactions occurring in cells cannot he reversed

117
Q

Non rechargeable cells: what will happen when the chemicals are used up

A

The battery will go flat and the emf will fall to 0.00V

118
Q

Non rechargeable cells: used in

A

Smoke detectors and clocks

119
Q

Non rechargeable cells: overall equation of zinc and manganese dioxide cell when it discharged

A

2MnO2 + 2H2O + Zn > 2MnO(OH) + 2OH- + Zn2+

120
Q

Non rechargeable cells: function of porous separator

A

Allows ions to flow

121
Q

Non rechargeable cells: function of carbon rod

A

Allows electrons to flow

122
Q

Non rechargeable cells: why cell often leaks after being used for a long time

A

Zn used up as reaction proceeds

123
Q

Rechargeable cells: why can they be recharged

A

Reaction occurring in cell can be reversed and chemicals in cell regenerated

124
Q

Rechargeable cells: examples

A
  • lead/acid- cars
  • Ni/Cd- torches/radios
  • lithium/ion-phones, tablets, cameras etc
125
Q

Lithium ion cells: why are they light

A

Lithium is the least dense mental

126
Q

Lithium ion cells: reaction occurring at positive electrode

A

Co(IV) reduced to Co(III)

127
Q

Lithium ion cells: reaction occurring at negative electrode

A

Li(0) oxidised to Li(+1)

128
Q

Lithium ion cells: equation for discharge of cell

A

CoO2 + Li > Li+[CoO2]-

129
Q

Lithium ion cells: equation for recharging cell

A

Discharge reaction reversed

Li+[CoO2]- > CoO2 + Li

130
Q

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Cu2+]<1moldm-3

A
  • equilibrium shift LHS
  • ECu less positive
  • Cu2+ will gain feevwr electrons
  • Ecell will decrease- cell has smaller difference in E
131
Q

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Zn2+]>1mol dm-3

A
  • equilibrium will shift RHS
  • EZn less negative
  • Zn will release fewer electrons
  • Ecell will decrease as cell has smaller difference in E
132
Q

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Zn2+] < 1moldm-3

A
  • equilibrium shift LHS
  • EZn become more negative
  • Zn will release more electrons
  • Ecell will increase as cell has a bigger difference in E
133
Q

if conditions are no longer standard what is cell potential written as as opposed to E0Cell

A

ECell

134
Q

Limitations of using electrode potentials tocpredict redox reactions

A
  • predictions using electrode potentials tell us about equilibrium but not RoR
  • many reactions in laboratory not done under standard conditions- will affect electrode potential vales
135
Q

Commercial applications of electrochemical cells: what 3 main types can cells be divided into

A
  • non- rechargeable cells
  • rechargeable cells
  • fuel cells
136
Q

Non rechargeable cells: how are they designed to be used only once

A

Reactions occurring in cells cannot he reversed

137
Q

Non rechargeable cells: what will happen when the chemicals are used up

A

The battery will go flat and the emf will fall to 0.00V

138
Q

Non rechargeable cells: used in

A

Smoke detectors and clocks

139
Q

Non rechargeable cells: overall equation of zinc and manganese dioxide cell when it discharged

A

2MnO2 + 2H2O + Zn > 2MnO(OH) + 2OH- + Zn2+

140
Q

Non rechargeable cells: function of porous separator

A

Allows ions to flow

141
Q

Non rechargeable cells: function of carbon rod

A

Allows electrons to flow

142
Q

Non rechargeable cells: why cell often leaks after being used for a long time

A

Zn used up as reaction proceeds

143
Q

Rechargeable cells: why can they be recharged

A

Reaction occurring in cell can be reversed and chemicals in cell regenerated

144
Q

Rechargeable cells: examples

A
  • lead/acid- cars
  • Ni/Cd- torches/radios
  • lithium/ion-phones, tablets, cameras etc
145
Q

Lithium ion cells: why are they light

A

Lithium is the least dense mental

146
Q

Lithium ion cells: reaction occurring at positive electrode

A

Co(IV) reduced to Co(III)

147
Q

Lithium ion cells: reaction occurring at negative electrode

A

Li(0) oxidised to Li(+1)

148
Q

Lithium ion cells: equation for discharge of cell

A

CoO2 + Li > Li+[CoO2]-

149
Q

Lithium ion cells: equation for recharging cell

A

Discharge reaction reversed

Li+[CoO2]- > CoO2 + Li

150
Q

Fuel cells: what does it use to create a voltage

A

Energy from the reaction of a fuel with oxygen

151
Q

Fuel cells: what flows into the fuel cell and what flows out

A

Fuel and oxygen flow into fuel cell and products flow out

152
Q

Fuel cells: what remains in the cell

A

The electrolyte

153
Q

Fuel cells: what can fuel cells operate continuously depending on

A

Provided the fuel and oxygen are supplied into cell

154
Q

Fuel cells: do fuel cells have to be recharged

A

No

155
Q

The alkaline hydrogen oxygen fuel cell: what are the cells two electrodes made out of

A

Porous Pt based material

156
Q

The alkaline hydrogen oxygen fuel cell: what are the two electrodes separated by

A

A semi permeable membrane

157
Q

The alkaline hydrogen oxygen fuel cell: what is the electrolyte

A

Sodium hydroxide solution

158
Q

The alkaline hydrogen oxygen fuel cell: which reaction takes place when hydrogen enters at the negative electrode

A

H2 + 2OH- > 2H2O + 2e-

159
Q

The alkaline hydrogen oxygen fuel cell: reaction taking place at positive electrode

A

O2 + 2H2O + 4e- > 4OH-

160
Q

The alkaline hydrogen oxygen fuel cell: overall equation

A

2H2 + O2 > 2H2O

161
Q

Advantages of fuel cells: why are they more efficient

A

They convert more of their available energy into kinetic energy

162
Q

Advantages of fuel cells: what is the only waste product

A

Water

163
Q

Advantages of fuel cells: why do they not need to be recharged

A

They produce a continuous supply of energy so long as hydrogen and oxygen are supplied so they do not need to be recharged

164
Q

Disadvantages of fuel cells: what is the disadvantage relating to hydrogen being produced

A

Can be done by electrolysis of water but requires electricity- burning fossil fuels

165
Q

Disadvantages of fuel cells: why must hydrogen be handled carefully when stored and transported

A

It’s explosive and flammable

166
Q

Disadvantages of fuel cells: what is there nothing of relating to hydrogen fuel

A

No infrastructure to provide hydrogen fuel for cars

Chemistry (42 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions