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REDOX Flashcards

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1
Q

What are oxidation and reduction reactions commonly known as?

A

Redox reactions

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2
Q

What occurs during oxidation?

A

Transfer of electrons to another substance (‘loss of electrons’)

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3
Q

What occurs during reduction?

A

Acceptance of electrons from another substance (‘gain of electrons’)

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4
Q

What is the substance that loses electrons said to be?

A

Oxidised

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5
Q

What is the substance that gains electrons said to be?

A

Reduced

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6
Q

What is an oxidant?

A

A species that causes another to be oxidised (itself reduced)

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7
Q

What is a reductant?

A

A species that causes another to be reduced (itself oxidised)

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8
Q

What is the overall reaction equation for the reaction between sodium and chlorine?

A

2 Na(s) + Cl2 (g) → 2 NaCl(s)

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9
Q

Complete the half-equation: Ba(s) → _______

A

Ba2+(s) + 2 e- (oxidation)

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10
Q

Complete the half-equation: O2 (g) → _______

A

O2-(s) (reduction)

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11
Q

What is the balanced oxidation half-equation for sodium?

A

2 Na(s) → 2 Na+(s) + 2 e-

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12
Q

What is the balanced reduction half-equation for chlorine?

A

Cl2 (g) + 2 e- → 2 Cl-(s)

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13
Q

True or False: Oxidation and reduction can occur independently.

A

False

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14
Q

What is the role of H+ ions in the reaction between zinc and hydrochloric acid?

A

They are reduced

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15
Q

What must be balanced in redox reactions?

A

The number of electrons lost and gained

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16
Q

What is the first step to balance complex redox reactions?

A

Start with one of the redox conjugate pairs

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17
Q

What is the oxidation number of an atom in its free elemental state?

A

Zero

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18
Q

What is the oxidation number of elements in simple ions equal to?

A

The charge on the ion

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19
Q

What is the oxidation state of oxygen in compounds?

A

-2

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20
Q

What is the oxidation state of hydrogen in compounds?

A

+1

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21
Q

What is the significance of oxidation numbers?

A

They help identify oxidisers and reducers in reactions

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22
Q

Complete the half-equation: Cu → _______

A

Cu2+ + 2 e- (oxidation)

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23
Q

What is the overall net ionic equation for the reaction of magnesium with sulfuric acid?

A

Mg(s) + 2 H+(aq) → Mg2+(aq) + H2(g)

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24
Q

What is the role of potassium permanganate in redox reactions?

A

It is a strong oxidant

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25
What happens to the oxidation number of an element in a redox reaction?
It changes
26
What is needed to determine whether a reaction is a redox reaction?
Oxidation numbers
27
What are the products of the reaction between iron (II) ions and acidified permanganate ions?
Iron (III) and manganese (II) ions
28
Complete the half-equation: N3− → _______
N2 (oxidation)
29
Complete the half-equation: SO42− → _______
SO2 (reduction)
30
What is the final step in balancing half-equations?
Add the two half-equations together and balance off electrons
31
What type of reaction is photosynthesis?
A redox reaction
32
What is an example of a redox reaction in everyday life?
Corrosion
33
What is the oxidation state of oxygen when present in molecular compounds?
-2 ## Footnote This applies to most compounds except for peroxides.
34
What is the oxidation state of hydrogen in molecular compounds?
+1 ## Footnote This applies to most compounds except for metal hydrides.
35
What is the sum of oxidation states in a neutral compound?
Zero
36
What is the sum of oxidation states in a polyatomic ion?
Equal to the charge of the ion
37
In which compounds does oxygen have an oxidation state of -1?
Peroxides ## Footnote Example: H2O2
38
In which compounds does hydrogen have an oxidation state of -1?
Metal hydrides ## Footnote Example: LiH
39
What indicates that oxidation has occurred in terms of oxidation number?
An increase in oxidation number
40
What indicates that reduction has occurred in terms of oxidation number?
A decrease in oxidation number
41
What is the definition of a redox reaction?
A reaction in which oxidation and reduction occur simultaneously
42
Amongst species containing the same element, which is usually the most powerful oxidiser?
The substance in the highest oxidation state
43
Amongst species containing the same element, which is usually the most powerful reducer?
The substance in the lowest oxidation state
44
What is the typical role of a substance with an intermediate oxidation state?
It may act as either an oxidiser or a reducer
45
Which is the most powerful oxidiser among the following: HClO, HClO2, HClO3, HClO4?
HClO4
46
Which is the most powerful reducer among the following: H2S, H2SO3, S8, Na2S2O3, H2SO4, H2S2O7?
H2S
47
What is the electrochemical series?
A comparative list of oxidisers and reducers based on experimental data
48
What does a positive EMF indicate?
A spontaneous reaction will occur
49
What is the standard reduction potential (E0)?
A measure of the tendency of a species to gain electrons
50
What happens in an electrochemical cell?
Electricity is produced from chemical change
51
What is the role of the salt bridge in an electrochemical cell?
To maintain electrical neutrality by allowing ion flow
52
What is the definition of oxidation in an electrochemical reaction?
Loss of electrons
53
What is the definition of reduction in an electrochemical reaction?
Gain of electrons
54
What are half-cells in an electrochemical cell?
Compartments where oxidation and reduction reactions occur
55
What is the cell EMF?
The potential difference between the half-cells
56
What is indicated by the E0 values in the electrochemical series?
The relative strength of oxidisers and reducers
57
Fill in the blank: In peroxides, the oxidation state of oxygen is ______.
-1
58
Fill in the blank: The oxidation state of hydrogen in metal hydrides is ______.
-1
59
True or False: The oxidiser is the species that is reduced in a redox reaction.
True
60
True or False: The reducer is the species that is oxidised in a redox reaction.
True
61
What are the two types of electrodes in an electrochemical cell?
The anode and cathode
62
What are the positive and negative electrodes referred to as?
The positive and negative electrodes
63
What is the direction of electron flow in the external circuit?
From the anode to the cathode
64
What is the direction of ion flow in the internal circuit, including the salt bridge?
Positive ions flow towards the cathode and negative ions flow towards the anode
65
What is the oxidiser? Fill in the blank: ____________
[key learning term]
66
What is the reducer? Fill in the blank: ____________
[key learning term]
67
What is the reaction in the anode half cell? Fill in the blank: _________________________________
[key learning term]
68
What is the reaction in the cathode half cell? Fill in the blank: _________________________________
[key learning term]
69
What is the overall reaction of this cell? Fill in the blank: _________________________________
[key learning term]
70
What is the cell EMF? Fill in the blank: _______________________________
[key learning term]
71
Suggest a suitable substance to place in the salt bridge. Fill in the blank: _________________________
[key learning term]
72
As the reaction proceeds, what happens to the anode?
The anode material is oxidized and decreases in mass
73
As the reaction proceeds, what happens to the cathode?
The cathode material is reduced and increases in mass
74
What happens to the Mg2+ solution as the reaction proceeds?
The concentration of Mg2+ decreases
75
What happens to the Pb2+ solution as the reaction proceeds?
The concentration of Pb2+ decreases
76
What must be true about the electrodes in certain half cells?
They must be inert, typically made from platinum or graphite
77
How is a half-cell represented in notation?
oxidiser|reducer
78
What is the general rule for half-cell notation?
The anode half-cell is on the left and the cathode half-cell follows
79
What does a single vertical line (|) represent in cell notation?
A phase boundary between two chemical species in contact
80
What does a double vertical line (||) represent in cell notation?
The salt bridge separating the half-cells
81
What is a primary cell?
A cell that cannot be recharged and needs to be replaced
82
What is a secondary cell?
A cell that can be recharged
83
List three common examples of primary cells
* Zinc-carbon dry cells * Alkaline cells * Button cells
84
List three common examples of secondary cells
* Lead-acid car batteries * Lithium ion cells * Nickel-cadmium cells
85
What is electrolysis?
The process of using electrical energy to drive a non-spontaneous redox reaction
86
What is an electrolytic cell?
The apparatus used to cause electrolysis
87
What is electroplating?
The deposition of a layer of metal on the surface of another metal through electrolysis
88
At the cathode during electroplating, what happens to silver ions?
Silver ions are reduced to metallic silver
89
At the anode during electroplating, what happens to the silver electrode?
Silver metal is oxidized to silver ions
90
What determines the products of electrolysis?
* The nature of the electrolyte * The relative strength of oxidisers and reducers * The concentration of the electrolyte * The acidity or alkalinity of the solution * The nature of the electrodes
91
What reactions occur in the electrolysis of molten sodium chloride?
Cathode: Na+(l) + e- → Na(l) Anode: 2 Cl-(l) → Cl2(g) + 2 e-
92
What will occur in the electrolysis of dilute aqueous sodium chloride with inert electrodes?
Water oxidizes and reduces preferentially over Na+ and Cl- ions
93
What happens to the products of electrolysis at high concentrations of sodium chloride?
Chlorine gas is likely produced at the anode
94
What happens to the products of electrolysis at low concentrations of sodium chloride?
Oxygen gas may be produced instead of chlorine
95
What is the purpose of using a simple table in predicting electrolysis products?
To list species present at the anode and cathode and determine likely reactions
96
What is the process of purification of copper by electrolysis?
Using copper(II) sulfate solution with impure copper anodes and pure copper cathodes
97
At the cathode during copper purification, what happens to copper(II) ions?
They are deposited as copper metal
98
At the anode during copper purification, what happens to copper?
Copper is oxidized to copper(II) ions
99
What is the electrolyte used in the purification of copper?
Copper(II) sulfate solution ## Footnote The electrolyte facilitates the transfer of copper ions during electrolysis.
100
What happens at the cathode during the electrolysis of copper?
Copper(II) ions are deposited as copper ## Footnote This process contributes to the increase in mass of the cathode.
101
What occurs at the anode during the electrolysis of copper?
Copper goes into solution as copper(II) ions ## Footnote This process depletes the mass of the anode.
102
What is anode sludge?
A mixture of metals that do not dissolve and unreactive material ## Footnote It forms from impurities in the impure copper anodes.
103
What is Faraday's first law of electrolysis?
The mass of substance produced at the electrodes is directly proportional to the quantity of charge (Q) flowing through the cell ## Footnote This law is fundamental in quantitative electrolysis calculations.
104
What is Faraday's constant?
96500 C mol-1 ## Footnote This value is used to calculate the charge associated with one mole of electrons.
105
What is the relationship between current, time, and charge in electrolysis?
Charge (Q) = Current (I) x Time (t) ## Footnote This formula is essential for quantifying electrolysis processes.
106
What happens to zinc ions during copper electrolysis?
Zinc ions can go into solution but may not be discharged at the cathode if their concentration is not too high ## Footnote This can affect the concentration of copper ions in the solution.
107
What is the oxidation reaction for iron during rusting?
Fe(s) → Fe2+(aq) + 2 e- ## Footnote This represents the loss of electrons during the corrosion process.
108
What is the reduction reaction for oxygen during rusting?
O2(g) + 2 H2O(l) + 4 e- → 4 OH-(aq) ## Footnote This reaction occurs in the presence of water and contributes to the formation of rust.
109
What are the effects of corrosion on metals?
* Decreased strength and elasticity * Brittle and weak oxide products * Increased volume of corrosion products * Electrical failures in car systems ## Footnote These effects can lead to significant structural and functional issues.
110
What is differential aeration in the context of corrosion?
Corrosion occurs preferentially where the concentration of oxygen is highest ## Footnote This phenomenon can lead to localized corrosion in metals.
111
What is cathodic protection?
A method to protect metals from corrosion by making them the cathode ## Footnote This can be achieved through impressed current or sacrificial anodes.
112
What is the role of a sacrificial anode?
It is a more reactive metal that oxidizes preferentially to protect the steel structure ## Footnote This method is commonly used in marine applications.
113
What is anodising in aluminum corrosion resistance?
A process that thickens the oxide layer on aluminum, enhancing its corrosion resistance ## Footnote It can also allow for coloring of the oxide layer.
114
What are the conditions that increase the rate of iron corrosion?
* Presence of an electrolyte * Impure iron * Iron in contact with less active metal * Iron under mechanical stress ## Footnote Each condition facilitates different aspects of the corrosion process.
115
What is the net ionic equation for the reaction of aluminum with nitric acid?
Al + 3 HNO3 → Al3+ + 3 NO2 + 3 H2O ## Footnote This represents the oxidation of aluminum and the reduction of nitric acid.
116
What is the balanced total equation for the reaction of aluminum with nitric acid?
4 Al + 12 HNO3 → 4 Al(NO3)3 + 3 NO2 + 6 H2O ## Footnote This shows the complete stoichiometry of the reaction.
117
What is the reduction reaction for Cr3+?
e- → Cr3+ + 4H20 ## Footnote This reaction shows the reduction of chromium ions in an aqueous environment.
118
What is the reduction reaction for BrO3-?
BrO3- + 3H+ + 2e- → HBrO2 + H20 ## Footnote This reaction describes the reduction of bromate ions.
119
What is the reduction reaction for SO42-?
SO42- + 4H+ + 2e- → SO2 + 2H20 ## Footnote This shows the reduction of sulfate ions to sulfur dioxide.
120
This shows the reduction of sulfate ions to sulfur dioxide.
V3+ + H20 → VO2+ + 2H+ + e- ## Footnote This reaction represents the oxidation of vanadium ions.
121
What is the reduction reaction for O2?
O2 + 4H+ + 4e- → 2H20 ## Footnote This illustrates the reduction of oxygen in an acidic solution.
122
What is the reduction reaction for S2O32-?
S2O32- + 6H+ + 4e- → 2S + 3H20 ## Footnote This reaction shows the reduction of thiosulfate ions to elemental sulfur.
123
What is the oxidation reaction for Al?
Al → Al3+ + 3e- ## Footnote This reaction depicts the oxidation of aluminum.
124
What is the reduction reaction for Sn2+?
Sn2+ + 2e- → Sn ## Footnote This shows the reduction of tin ions.
125
What is the non-redox reaction involving Al and Sn2+?
2Al + 3Sn2+ → 2Al3+ + 3Sn ## Footnote This reaction represents a non-redox exchange between aluminum and tin ions.
126
What is the oxidation reaction for Cl-?
2Cl- → Cl2 + 2e- ## Footnote This illustrates the oxidation of chloride ions.
127
What is the reduction reaction for MnO4-?
MnO4- + 8H+ + 5e- → Mn2+ + 4H20 ## Footnote This shows the reduction of permanganate ions.
128
What is the non-redox reaction involving Cl- and MnO4-?
10Cl- + 2MnO4- + 16H+ → 5Cl2 + 2Mn2+ + 8H20 ## Footnote This reaction depicts a non-redox process involving chlorine and permanganate.
129
What is the oxidation reaction for SO2?
SO2 + 2H2O → SO42- + 4H+ + 2e- ## Footnote This reaction represents the oxidation of sulfur dioxide.
130
What is the reduction reaction for HNO3?
HNO3 + H+ + e- → NO2 + H20 ## Footnote This shows the reduction of nitric acid.
131
What is the non-redox reaction involving HNO3 and SO2?
2HNO3 + SO2 → SO42- + 2NO2 + 2H+ ## Footnote This illustrates a non-redox reaction between nitric acid and sulfur dioxide.
132
What is the oxidation reaction for Fe2+?
Fe2+ → Fe3+ + e- ## Footnote This shows the oxidation of ferrous iron.
133
What is the reduction reaction for Cr2O72-?
Cr2O72- + 14H+ + 6e- → 2Cr3+ + 7H2O ## Footnote This indicates the reduction of dichromate ions.
134
What is the non-redox reaction involving Cr2O72- and Fe2+?
Cr2O72- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O ## Footnote This reaction depicts a non-redox process involving dichromate and ferrous iron.
135
What is the oxidation reaction for N2O?
N2O + 3H2O → 2NO2 + 6H+ + 6e- ## Footnote This shows the oxidation of nitrous oxide.
136
What is the reduction reaction for H2O2?
H2O2 + 2H+ + 2e- → 2H2O ## Footnote This illustrates the reduction of hydrogen peroxide.
137
What is the non-redox reaction involving H2O2 and N2O?
3H2O2 + N2O → 2NO2 + 3H2O ## Footnote This represents a non-redox reaction between hydrogen peroxide and nitrous oxide.
138
What is the oxidation reaction for Cr3+?
Cr3+ + 4H2O → CrO42- + 8H+ + 3e- ## Footnote This shows the oxidation of chromium ions.
139
What is the reduction reaction for Br2?
Br2 + 2e- → 2Br- ## Footnote This illustrates the reduction of bromine.
140
What is the non-redox reaction involving Br2 and Cr3+?
3Br2 + 2Cr3+ + 8H2O → 6Br- + 2CrO42- + 16H+ ## Footnote This reaction depicts a non-redox process involving bromine and chromium ions.
141
What is the oxidation reaction for SO2 with H2O?
SO2 + H2O → SO3 + 2H+ + 2e- ## Footnote This shows the oxidation of sulfur dioxide in the presence of water.
142
What is the reduction reaction for Au+?
Au+ + e- → Au ## Footnote This illustrates the reduction of gold ions.
143
What is the non-redox reaction involving SO2 and Au+?
SO2 + 2Au+ + H2O → SO3 + 2Au + 2H+ ## Footnote This reaction depicts a non-redox process involving sulfur dioxide and gold ions.
144
What is the oxidation reaction for GeO2?
GeO2 + 2H2O → GeO42- + 4H+ + 2e- ## Footnote This shows the oxidation of germanium dioxide.
145
What is the reduction reaction for Cl2?
Cl2 + 2e- → 2Cl- ## Footnote This illustrates the reduction of chlorine.
146
What is the non-redox reaction involving GeO2 and Cl2?
GeO2 + Cl2 + 2H2O → GeO42- + 2Cl- + 4H+ ## Footnote This reaction depicts a non-redox process involving germanium dioxide and chlorine.
147
What is the oxidation reaction for Fe?
Fe → Fe2+ + 2e- ## Footnote This shows the oxidation of iron.
148
What is the reduction reaction for Fe3+?
Fe3+ + e- → Fe2+ ## Footnote This illustrates the reduction of ferric iron.
149
What is the non-redox reaction involving Fe and Fe3+?
Fe + 2Fe3+ → 3Fe2+ ## Footnote This reaction depicts a non-redox process involving iron.
150
What is the oxidation reaction for Sn(OH)42-?
Sn(OH)42- + 4H+ → Sn4+ + 4H2O + 2e- ## Footnote This shows the oxidation of stannate ions.
151
What is the reduction reaction for MnO4- with H+?
MnO4- + 4H+ + 2e- → MnO2 + 2H20 ## Footnote This illustrates the reduction of permanganate to manganese dioxide.
152
What is the non-redox reaction involving MnO4- and Sn(OH)42-?
MnO4- + Sn(OH)42- + 8H+ → MnO2 + Sn4+ + 6H20 ## Footnote This reaction depicts a non-redox process involving permanganate and stannate.
153
What is the oxidation reaction for NH4+?
2NH4+ → N2 + 8H+ + 6e- ## Footnote This shows the oxidation of ammonium ions.
154
What is the reduction reaction for S2O32-?
S2O32- + 6H+ + 4e- → 2S + 3H20 ## Footnote This illustrates the reduction of thiosulfate ions.
155
What is the non-redox reaction involving NH4+ and S2O32-?
4NH4+ + 3S2O32- + 2H+ → 2N2 + 6S + 9H20 ## Footnote This reaction depicts a non-redox process involving ammonium and thiosulfate.
156
What is the oxidation reaction for V with H2O?
V + 2H20 → VO2+ + 4H+ + 5e- ## Footnote This shows the oxidation of vanadium in the presence of water.
157
What is the reduction reaction for NO3-?
NO3- + 3H+ + 2e- → HNO2 + H20 ## Footnote This illustrates the reduction of nitrate ions.
158
What is the non-redox reaction involving NO3- and V?
5NO3- + 2V + 7H+ → 2VO2+ + 5HNO2 + H20 ## Footnote This reaction depicts a non-redox process involving nitrate and vanadium.
159
What are the oxidation states listed in Set E?
+4, +6, +7, +5, +3, 0, +5, +7, +5, +1, +3, +4 ## Footnote These oxidation states correspond to various chemical species.
160
What are some examples of species in Set F?
Fe3+, Fe, HClO4, H2S, oxidation, reduction, non-redox ## Footnote This set includes various species and their classifications in redox chemistry.

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