Gen Chem - Redox and Electrochemistry Flashcards
(104 cards)
1
Q
What is the oxidation number of a free element?
A
The oxidation number of a free element is zero.
For example, the atoms in N2, P4, Sg, and He all have oxidation numbers of zero.
2
Q
What is the oxidation number for a monatomic ion?
A
The oxidation number for a monatomic ion is equal to the charge of the ion.
For example, the oxidation numbers for Na+, Cu+, Fe3+, Cl-, and N3- are +1, +2, +3, -1, and -3, respectively.
3
Q
What is the oxidation number of Group IA elements in a compound?
A
The oxidation number of each Group IA element in a compound is +1.
4
Q
What is the oxidation number of Group IIA elements in a compound?
A
The oxidation number of each Group IIA element in a compound is +2.
5
Q
What is the oxidation number of Group VIIA (halogens) elements in a compound?
A
The oxidation number of each Group VIIA element in a compound is -1, except when combined with an element of higher electronegativity.
For example, in HCl, the oxidation number of Cl is -1; in HOCl, however, the oxidation number of Cl is +1.
6
Q
What is the usual oxidation number of hydrogen?
A
The oxidation number of hydrogen is usually +1; however, it is -1 in compounds with less electronegative elements (Groups IA and IIA).
Hydrogen is +1 in HCl, but -1 in NaH.
7
Q
What is the oxidation number of oxygen in most compounds?
A
In most compounds, the oxidation number of oxygen is -2.
The exceptions are peroxides (O2^2-), where each oxygen is -1, and compounds with more electronegative elements, such as OF2, where oxygen has a +2 charge.
8
Q
What is the sum of the oxidation numbers in a neutral compound?
A
The sum of the oxidation numbers of all the atoms present in a neutral compound is zero.
9
Q
What is the sum of the oxidation numbers in a polyatomic ion?
A
The sum of the oxidation numbers of the atoms present in a polyatomic ion is equal to the charge of the ion.
Thus, for SO4^2-, the sum of the oxidation numbers must be -2.
10
Q
How can you think of the oxidation number?
A
Think of the oxidation number as the typical charge of an element based on its atomic number metallicity.
11
Q
What are oxidizing agents?
A
Substances that gain electrons in a chemical reaction
Examples include F2, Cl2, Br2, I2 (halogens), H2SO4, and KMnO4.
12
Q
What are reducing agents?
A
Substances that lose electrons in a chemical reaction
Examples include Sn2+, pure metals, and NaBH4.
13
Q
List three examples of halogen oxidizing agents.
A
- F2
- Cl2
- Br2
- I2
14
Q
What is the chemical formula for sulfuric acid?
A
H2SO4
15
Q
What type of substance is hydrazine?
A
A reducing agent
Commonly used in various chemical reactions.
16
Q
What is the role of NaClO in chemical reactions?
A
Acts as an oxidizing agent
17
Q
What is the significance of Zn (Hg) in organic chemistry?
A
Used as a reducing agent
Often utilized in reduction reactions.
18
Q
What is Lindlar’s catalyst used for?
A
Facilitates hydrogenation reactions
Commonly used to convert alkynes to alkenes.
19
Q
What does CrO3 indicate in chemical reactions?
A
An oxidizing agent
Often used in oxidation reactions.
20
Q
What does NaBH4 stand for?
A
Sodium borohydride
A common reducing agent in organic synthesis.
21
Q
What are NAD+ and FADH2 classified as?
A
Coenzymes that act as electron carriers
Involved in cellular respiration.
22
Q
Fill in the blank: F2, Cl2, Br2, and I2 are examples of _______.
A
oxidizing agents
23
Q
What is the function of LiAlH4 in chemical reactions?
A
Acts as a strong reducing agent
24
Q
What does PCC stand for?
A
Pyridinium chlorochromate
Used for oxidation of alcohols.
25
True or False: HNO3 is an oxidizing agent.
True
26
What do NADH and FADH2 represent?
Reduced forms of NAD+ and FAD
## Footnote
Play key roles in metabolic pathways.
27
What is oxidation in the context of redox reactions?
A loss of electrons
## Footnote
Oxidation refers to the process where an atom, ion, or molecule loses electrons.
28
What is reduction in the context of redox reactions?
A gain of electrons
## Footnote
Reduction involves the gain of electrons by an atom, ion, or molecule.
29
What is a redox reaction?
An oxidation-reduction reaction
## Footnote
Redox reactions involve the transfer of electrons between two species.
30
What role does an oxidizing agent play in a redox reaction?
Facilitates the oxidation of another compound and is reduced itself
## Footnote
The oxidizing agent accepts electrons during the reaction.
31
What role does a reducing agent play in a redox reaction?
Facilitates the reduction of another compound and is oxidized itself
## Footnote
The reducing agent donates electrons during the reaction.
32
Fill in the blank: Common oxidizing agents almost all contain _______.
[oxygen or a similarly electronegative element]
## Footnote
This characteristic allows them to accept electrons easily.
33
Fill in the blank: Common reducing agents often contain _______.
[metal ions or hydrides (HT)]
## Footnote
These substances are prone to lose electrons easily.
34
What is the most common method for balancing redox reactions?
Half-reaction method (ion-electron method)
## Footnote
This method involves separating and balancing two half-reactions.
35
What is the first step in balancing redox reactions using the half-reaction method?
Separate the two half-reactions
## Footnote
This allows for individual balancing of each half-reaction.
36
When balancing redox reactions, which elements should be balanced first?
All elements besides H and O
## Footnote
This prioritization helps simplify the balancing process.
37
In acidic solutions, how should H and O be balanced?
Using water and H+
## Footnote
Water is added to balance oxygen, and H+ ions are used to balance hydrogen.
38
In basic solutions, how should H and O be balanced?
Using water and OH-
## Footnote
Hydroxide ions are used to balance hydrogen in basic conditions.
39
What is the purpose of adding electrons in balancing half-reactions?
To balance the charges of each half-reaction
## Footnote
Electrons are added to one side of the reaction as needed.
40
What must be done to the half-reactions to balance the number of electrons?
Multiply the half-reactions as necessary
## Footnote
This ensures both half-reactions have the same number of electrons.
41
What is the final step after adding the half-reactions?
Confirm that the mass and charge are balanced
## Footnote
This verification is crucial to ensure the reaction is correctly balanced.
42
What does a complete ionic equation account for?
All of the ions present in a reaction
## Footnote
Aqueous compounds are split into their relevant ions while solid salts remain intact.
43
What do net ionic equations ignore?
Spectator ions
## Footnote
These are the ions that do not participate in the reaction.
44
How is a net ionic reaction obtained?
Subtract the ions appearing on both sides of the reaction
## Footnote
This process removes spectator ions from the complete ionic equation.
45
What is generally true about net ionic equations for reactions with no aqueous salts?
They are the same as the overall balanced reaction
## Footnote
This indicates that all species are involved in the reaction.
46
What is true about double displacement (metathesis) reactions that do not form a solid salt?
There is no net ionic reaction
## Footnote
In such cases, all ions remain in solution and do not change oxidation number.
47
What is the most common method for balancing redox reactions?
Half-reaction method (ion-electron method)
## Footnote
This method involves separating and balancing two half-reactions.
48
What is the first step in balancing redox reactions using the half-reaction method?
Separate the two half-reactions
## Footnote
This allows for individual balancing of each half-reaction.
49
When balancing redox reactions, which elements should be balanced first?
All elements besides H and O
## Footnote
This prioritization helps simplify the balancing process.
50
In acidic solutions, how should H and O be balanced?
Using water and H+
## Footnote
Water is added to balance oxygen, and H+ ions are used to balance hydrogen.
51
In basic solutions, how should H and O be balanced?
Using water and OH-
## Footnote
Hydroxide ions are used to balance hydrogen in basic conditions.
52
What is the purpose of adding electrons in balancing half-reactions?
To balance the charges of each half-reaction
## Footnote
Electrons are added to one side of the reaction as needed.
53
What must be done to the half-reactions to balance the number of electrons?
Multiply the half-reactions as necessary
## Footnote
This ensures both half-reactions have the same number of electrons.
54
What is the final step after adding the half-reactions?
Confirm that the mass and charge are balanced
## Footnote
This verification is crucial to ensure the reaction is correctly balanced.
55
What does a complete ionic equation account for?
All of the ions present in a reaction
## Footnote
Aqueous compounds are split into their relevant ions while solid salts remain intact.
56
What do net ionic equations ignore?
Spectator ions
## Footnote
These are the ions that do not participate in the reaction.
57
How is a net ionic reaction obtained?
Subtract the ions appearing on both sides of the reaction
## Footnote
This process removes spectator ions from the complete ionic equation.
58
What is generally true about net ionic equations for reactions with no aqueous salts?
They are the same as the overall balanced reaction
## Footnote
This indicates that all species are involved in the reaction.
59
What is true about double displacement (metathesis) reactions that do not form a solid salt?
There is no net ionic reaction
## Footnote
In such cases, all ions remain in solution and do not change oxidation number.
60
What are electrochemical cells?
Contained systems in which oxidation-reduction reactions occur
## Footnote
Electrochemical cells convert chemical energy into electrical energy and vice versa.
61
What are the three fundamental types of electrochemical cells?
Galvanic cells, electrolytic cells, concentration cells
## Footnote
Galvanic cells are also known as voltaic cells.
62
What type of reactions do galvanic cells and concentration cells house?
Spontaneous reactions
## Footnote
These reactions occur naturally without external energy input.
63
What type of reactions do electrolytic cells contain?
Nonspontaneous reactions
## Footnote
These reactions require external energy to occur.
64
What does the change in Gibbs free energy (ΔG) indicate about spontaneity?
ΔG < 0 indicates spontaneity; ΔG > 0 indicates nonspontaneity
## Footnote
Spontaneous reactions release energy, while nonspontaneous reactions absorb energy.
65
What are the electrodes in electrochemical cells where oxidation and reduction occur called?
Anode (oxidation) and cathode (reduction)
## Footnote
The anode is where electrons are lost, and the cathode is where electrons are gained.
66
What does electromotive force (emf) correspond to in electrochemical cells?
Voltage or electrical potential difference of the cell
## Footnote
Emf reflects the capacity of the cell to do electrical work.
67
What does a positive emf indicate about an electrochemical cell?
The cell is able to release energy (ΔG < 0), meaning it is spontaneous
## Footnote
Positive emf indicates that the cell can perform work.
68
What does a negative emf indicate about an electrochemical cell?
The cell must absorb energy (ΔG > 0), meaning it is nonspontaneous
## Footnote
Negative emf indicates that the cell cannot perform work without external energy.
69
What are electrochemical cells?
Contained systems in which oxidation-reduction reactions occur
## Footnote
Electrochemical cells convert chemical energy into electrical energy and vice versa.
70
What are the three fundamental types of electrochemical cells?
Galvanic cells, electrolytic cells, concentration cells
## Footnote
Galvanic cells are also known as voltaic cells.
71
What type of reactions do galvanic cells and concentration cells house?
Spontaneous reactions
## Footnote
These reactions occur naturally without external energy input.
72
What type of reactions do electrolytic cells contain?
Nonspontaneous reactions
## Footnote
These reactions require external energy to occur.
73
What does the change in Gibbs free energy (ΔG) indicate about spontaneity?
ΔG < 0 indicates spontaneity; ΔG > 0 indicates nonspontaneity
## Footnote
Spontaneous reactions release energy, while nonspontaneous reactions absorb energy.
74
What are the electrodes in electrochemical cells where oxidation and reduction occur called?
Anode (oxidation) and cathode (reduction)
## Footnote
The anode is where electrons are lost, and the cathode is where electrons are gained.
75
What does electromotive force (emf) correspond to in electrochemical cells?
Voltage or electrical potential difference of the cell
## Footnote
Emf reflects the capacity of the cell to do electrical work.
76
What does a positive emf indicate about an electrochemical cell?
The cell is able to release energy (ΔG < 0), meaning it is spontaneous
## Footnote
Positive emf indicates that the cell can perform work.
77
What does a negative emf indicate about an electrochemical cell?
The cell must absorb energy (ΔG > 0), meaning it is nonspontaneous
## Footnote
Negative emf indicates that the cell cannot perform work without external energy.
78
What is the free energy change that represents a non-spontaneous reaction?
+120 kJ
79
What does the Nernst equation calculate?
The emf of a cell under nonstandard conditions.
80
What is the relationship between emf and ionic concentrations in electrochemical cells?
Emf varies with the changing concentrations of the species in the cell.
81
What is the standard form of the Nernst equation?
Ecell = E°cell - (RT/nF) ln Q
82
In the simplified Nernst equation, what assumption is made about temperature?
T = 298 K
83
What is the simplified version of the Nernst equation?
Ecell = E°cell - (0.0592/n) log Q
84
What variables are represented in the Nernst equation?
* Ecell
* E°cell
* R (ideal gas constant)
* T (temperature in kelvin)
* n (number of moles of electrons)
* F (Faraday constant)
* Q (reaction quotient)
85
True or False: The emf of a cell is constant regardless of conditions.
False
86
Fill in the blank: The reaction quotient, Q, is used in the Nernst equation to account for _______.
[the concentration of ions in the cell]
87
What does a concentration cell require for a measurable voltage and current?
Different concentrations of ions in the two compartments.
88
What is the free energy change that represents a non-spontaneous reaction?
+120 kJ
89
What does the Nernst equation calculate?
The emf of a cell under nonstandard conditions.
90
What is the relationship between emf and ionic concentrations in electrochemical cells?
Emf varies with the changing concentrations of the species in the cell.
91
What is the standard form of the Nernst equation?
Ecell = E°cell - (RT/nF) ln Q
92
In the simplified Nernst equation, what assumption is made about temperature?
T = 298 K
93
What is the simplified version of the Nernst equation?
Ecell = E°cell - (0.0592/n) log Q
94
What variables are represented in the Nernst equation?
* Ecell
* E°cell
* R (ideal gas constant)
* T (temperature in kelvin)
* n (number of moles of electrons)
* F (Faraday constant)
* Q (reaction quotient)
95
True or False: The emf of a cell is constant regardless of conditions.
False
96
Fill in the blank: The reaction quotient, Q, is used in the Nernst equation to account for _______.
[the concentration of ions in the cell]
97
What does a concentration cell require for a measurable voltage and current?
Different concentrations of ions in the two compartments.
98
How can AG° be determined?
AG° can be determined using the equation: AG° = -RT ln Keq
## Footnote
Where R is the ideal gas constant, T is the absolute temperature, and Keq is the equilibrium constant for the reaction.
99
What is the relationship between AG°, E° cell, and Keq?
AG° = -nFE° cell = -RT ln Keq
## Footnote
This shows that the standard free energy change is related to both the cell potential and the equilibrium constant.
100
What variables are needed to calculate E° cell?
Values for n, T, and Keq are needed to calculate E° cell
## Footnote
n is the number of moles of electrons transferred, T is the temperature in Kelvin, and Keq is the equilibrium constant.
101
What can be inferred about logarithm values in relation to equilibrium constants?
A logarithm will be positive when equilibrium constants are greater than 1
## Footnote
This indicates that the reaction favors the products at equilibrium.
102
Is it necessary to calculate natural logarithm values on the MCAT?
No, you will not be expected to calculate natural logarithm values in your head
## Footnote
However, understanding the concepts behind these equations is important for the exam.
103
Fill in the blank: AG° can also be expressed as _______.
AG° = -RT ln Keq
104
True or False: AG° and E° cell are inversely related.
True
## Footnote
As one increases, the other decreases, indicating a relationship between free energy and cell potential.
