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Questions and Answers
In an electrochemical series, if $\Delta G$ for the reduction of $A^+$ to $A$ is more negative than that of $B^+$ to $B$, what can be inferred?
In an electrochemical series, if $\Delta G$ for the reduction of $A^+$ to $A$ is more negative than that of $B^+$ to $B$, what can be inferred?
- The reduction of $B^+$ to $B$ is more spontaneous than $A^+$ to $A$
- $A^+$ is a stronger oxidizing agent than $B^+$ (correct)
- $A$ is a stronger reducing agent than $B$
- $B^+$ is a stronger oxidizing agent than $A^+$
What is the significance of a Latimer diagram in electrochemistry?
What is the significance of a Latimer diagram in electrochemistry?
- It provides a visual representation of standard reduction potentials for various redox states of an element (correct)
- It predicts the equilibrium constant of a redox reaction
- It quantifies the rate of electron transfer in electrochemical reactions
- It illustrates the pH dependence of electrochemical processes
In a Frost diagram, how does a steeper line connecting two redox states relate to oxidizing strength?
In a Frost diagram, how does a steeper line connecting two redox states relate to oxidizing strength?
- A steeper line indicates a stronger oxidizing agent. (correct)
- A steeper line indicates a weaker oxidizing agent.
- The slope of the line indicates the rate of the reaction.
- The steepness of the line is unrelated to oxidizing strength.
What information can be obtained from Pourbaix diagrams?
What information can be obtained from Pourbaix diagrams?
In a galvanic cell, when does the flow of electrons cease, and what is the state of the cell at that point?
In a galvanic cell, when does the flow of electrons cease, and what is the state of the cell at that point?
What is the purpose of a salt bridge or a semipermeable membrane in an electrochemical cell?
What is the purpose of a salt bridge or a semipermeable membrane in an electrochemical cell?
In the context of fuel cells, what condition determines the thermodynamic threshold cell potential?
In the context of fuel cells, what condition determines the thermodynamic threshold cell potential?
What is a key difference between a galvanic cell and an electrolytic cell?
What is a key difference between a galvanic cell and an electrolytic cell?
In solid-state batteries, what role does the electrolyte play, and what is a common material used in lithium-ion batteries?
In solid-state batteries, what role does the electrolyte play, and what is a common material used in lithium-ion batteries?
What does the Ellingham diagram primarily illustrate, and what is its significance in materials science?
What does the Ellingham diagram primarily illustrate, and what is its significance in materials science?
Flashcards
Frost Diagram
Frost Diagram
A diagram correlating the ΔG value with a particular redox process, useful for assessing the stability of oxidation states.
Latimer Diagram
Latimer Diagram
A diagram showing the relationship between standard redox potential and redox states of a substance.
Pourbaix Diagram
Pourbaix Diagram
Diagrams showing the stability of various oxidation states in aqueous media, considering pH dependence.
Fuel Cell
Fuel Cell
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Galvanic Cell
Galvanic Cell
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Ellingham Diagram
Ellingham Diagram
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Error
Error
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Precision
Precision
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Accuracy
Accuracy
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Study Notes
- Formal Potential Changes concern purely homogeneous redox electrochemical series.
Reaction Equations
- A + B ⇄ C + D
- A + ne- ⇄ C, ΔG = -nFE°A/C
- B + ne- ⇄ D, ΔG = -nFE°B/D
- ΔG_rxn = -ΔG_B/D + ΔG_A/C = nF(E°_A/C - E°_B/D)
At Equilibrium
- ΔG_rxn = 0, leading to E°_A/C - E°_B/D = (RT/nF) * ln([A][B]/[C][D])
- ln([A][B]/[C][D]) = (nF/RT)*(E°_A/C - E°_B/D)
- The equilibrium constant, lnK_eq, can be expressed as (nF/RT)*(E°_A/C - E°_B/D)
Disproportionation and Comproportionation Reactions
- Explains reactions where a particular atom has multiple redox states.
Latimer Diagram
- Correlation diagram between standard redox potential and redox states.
- Includes example of Nitrogen at different oxidation states:
- NO₃⁻ (+5) → N₂O₄ (+4) → HNO₂ (+3) → NO (+2) → N₂0 (+1) → N₂ (0) → NH₂OH (-1) → NH₄⁺ (-3).
Determinations
- Standard reduction potential determined for any number of electron transfers.
- Simple addition or subtraction of reduction potentials followed by dividing with the number of electrons.
Frost Diagram
- Diagram correlates the nE° value with oxidation states.
- nE° is on the y-axis against oxidation state on the x-axis.
- A + 2 → A-
- Example of Bromine redox states:
- BrO₄⁻ (+7) → BrO₃⁻ (+5) → BrO⁻ (+1) → Br₂ (0) → Br⁻ (-1)
- E°(A/A) can be calculated using E° = (n₁F₁ + n₂F₂)/(n₁+n₂)
- To construct a Frost diagram, start with a Latimer diagram for reference
Key Properties
- Stiffer lines indicate a more oxidizing nature.
- Displays stability of various oxidation states in aqueous media and their pH dependence.
Iron Compound Overview
- Fe(m) → Fe²⁺ + 2e⁻
- Fe²⁺ + 6H₂O → [Fe(H₂O)₆]²⁺
Redox Reactions and Applications
- Redox reactions drive the flow of electrons or generation of electricity in solutions.
Daniel Cells.
- Redox couple A: A + e⁻ → A⁻
- Redox couple B: B + e⁻ → B⁻
Redox Reaction Condition
- E₁ > E₂; A⁺ → A; B⁻ → B.
- The reaction stops (ΔE = 0) upon reaching equilibrium; no electron flow occurs.
Galvanic Cell
- Until reactants are consumed, the flow of electrons occurs - Galvanic cell
- B/B⁺ || A/A⁻ spontaneous electronic cell.
- Examples: Mg/Mg²⁺ || Cu²⁺/Cu and Zn/Zn²⁺ || Cu²⁺/Cu.
Electrode Potentials
- Alters the chemical reactions
- Application of a potential reverses electron direction, ΔE < 0 for non-spontaneous reactions.
Fuel Cells
- 2H₂ + O₂ → 2H₂O ⇄ 2H⁺ + 2OH⁻ ⇄ 2H⁺ + O²⁻
- O²⁻ can be associated with H⁺ ions.
Fuel Cell Thermodynamics
- ΔE = 1.23 - 0.06pH
Electrochemical Cells
- Requires an electrolytic solution/electrolyte separated by a membrane.
- Non-connected cells maintain potential differences.
Lithium-Ion Batteries
- Anode: Li → Li⁺ + e⁻
- Cathode: Li⁺ + e⁻ → Li
- The Nernst Equation predicts if a reaction will happen.
- For the reaction A+B-->C+D, determine if K >Q
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