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What effect does increasing the size of ions have on conductance?
What effect does increasing the size of ions have on conductance?
How does the viscosity of a solvent affect ionic mobility?
How does the viscosity of a solvent affect ionic mobility?
What does a high dielectric constant in a solvent indicate?
What does a high dielectric constant in a solvent indicate?
According to Coulomb's law, what happens to the force between two charged particles as the distance increases?
According to Coulomb's law, what happens to the force between two charged particles as the distance increases?
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How does the concentration of an electrolyte impact specific conductance?
How does the concentration of an electrolyte impact specific conductance?
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What is the effect of low dielectric constant solvents on conductance?
What is the effect of low dielectric constant solvents on conductance?
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In the context of ionic conductance, what happens to the ionization of electrolytes in solvents with high dielectric constants?
In the context of ionic conductance, what happens to the ionization of electrolytes in solvents with high dielectric constants?
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What occurs during the initial small current observed before point b in the current-potential curve?
What occurs during the initial small current observed before point b in the current-potential curve?
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What describes the current behavior after point c in the current-potential curve?
What describes the current behavior after point c in the current-potential curve?
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What is the value of the decomposition potential for most aqueous solutions of acids and bases?
What is the value of the decomposition potential for most aqueous solutions of acids and bases?
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What does the equation Di = D0 + η represent in electrolysis?
What does the equation Di = D0 + η represent in electrolysis?
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Which reaction occurs at the cathode in acidic solutions during electrolysis?
Which reaction occurs at the cathode in acidic solutions during electrolysis?
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What characterizes the linear variation region at the electrode interface?
What characterizes the linear variation region at the electrode interface?
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In the equation $ψM - ψB = (ψM - ψH) + (ψH - ψB)$, what does $ψM$ represent?
In the equation $ψM - ψB = (ψM - ψH) + (ψH - ψB)$, what does $ψM$ represent?
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What happens to the potential across the electrified interface when charge on the metal surface increases?
What happens to the potential across the electrified interface when charge on the metal surface increases?
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Which capacity is defined as the ability of the region between the metal and the Helmholtz plane to store charge?
Which capacity is defined as the ability of the region between the metal and the Helmholtz plane to store charge?
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How can total capacity of the interface $ct$ be expressed mathematically based on capacities $cH$ and $cG$?
How can total capacity of the interface $ct$ be expressed mathematically based on capacities $cH$ and $cG$?
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What does $ψH$ signify in the potential variation equation?
What does $ψH$ signify in the potential variation equation?
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What does the term $d(ψM - ψB)/dqM$ demonstrate according to the equations provided?
What does the term $d(ψM - ψB)/dqM$ demonstrate according to the equations provided?
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What do thermal forces influence in the context of the potential variation?
What do thermal forces influence in the context of the potential variation?
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What does $ψB$ represent in the potential variation equation?
What does $ψB$ represent in the potential variation equation?
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Which capacity corresponds to the diffuse-charge capacity?
Which capacity corresponds to the diffuse-charge capacity?
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What occurs when the chemical potential of ions at solid state is greater than that in solution during the formation of the electric double layer?
What occurs when the chemical potential of ions at solid state is greater than that in solution during the formation of the electric double layer?
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In the second case of electric double layer formation, why is there an attraction of K+ ions to a negatively charged mercury electrode?
In the second case of electric double layer formation, why is there an attraction of K+ ions to a negatively charged mercury electrode?
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What is the condition when no electric double layer is formed during the interaction of metal with electrolyte?
What is the condition when no electric double layer is formed during the interaction of metal with electrolyte?
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Which of the following statements is true regarding the adsorption of ions on a neutral metallic surface?
Which of the following statements is true regarding the adsorption of ions on a neutral metallic surface?
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What happens if the chemical potential of Ag+ in solution is greater than that of Ag metal?
What happens if the chemical potential of Ag+ in solution is greater than that of Ag metal?
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What is a possible formation mechanism of the electric double layer due to the presence of dipolar molecules?
What is a possible formation mechanism of the electric double layer due to the presence of dipolar molecules?
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Why is it important to apply a potential within a certain range to the mercury electrode in an electrolyte?
Why is it important to apply a potential within a certain range to the mercury electrode in an electrolyte?
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In the scenario where a metal dissolves, which ions would it primarily attract from the solution after oxidation?
In the scenario where a metal dissolves, which ions would it primarily attract from the solution after oxidation?
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What type of interaction primarily influences the formation of the electric double layer with specific ions on metal surfaces?
What type of interaction primarily influences the formation of the electric double layer with specific ions on metal surfaces?
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What happens to the value of γ with an increase in the concentration of electrolyte according to experimental data?
What happens to the value of γ with an increase in the concentration of electrolyte according to experimental data?
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According to Helmholtz-Perrin theory, what is predicted about the capacity with a change in potential?
According to Helmholtz-Perrin theory, what is predicted about the capacity with a change in potential?
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What is the observed behavior of colloidal particles in relation to the dispersion medium?
What is the observed behavior of colloidal particles in relation to the dispersion medium?
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What interaction is responsible for the attraction of oppositely charged ions to an electrode?
What interaction is responsible for the attraction of oppositely charged ions to an electrode?
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What is the primary assumption of the Gouy-Chapman model regarding the double layer?
What is the primary assumption of the Gouy-Chapman model regarding the double layer?
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What can be said about the net charge in the bulk solution near an electrode?
What can be said about the net charge in the bulk solution near an electrode?
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What effect do thermal energy forces have on the motion of ions in solution?
What effect do thermal energy forces have on the motion of ions in solution?
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How do the electrocapillary curves demonstrate the relationship between cdl and electrolyte concentration?
How do the electrocapillary curves demonstrate the relationship between cdl and electrolyte concentration?
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What causes the repulsion of charges that have similar signs near an electrode?
What causes the repulsion of charges that have similar signs near an electrode?
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What discrepancy exists between Helmholtz-Perrin theory and experimental observations regarding capacity?
What discrepancy exists between Helmholtz-Perrin theory and experimental observations regarding capacity?
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Study Notes
Irreversible Electrochemistry (C 352)
- Electrochemistry: The branch of physical chemistry concerned with ionic conductors (electrolytes) and phenomena at their interfaces with electronic conductors (electrodes).
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Metallic vs. Electrolytic Conduction:
- Metallic: Electrical flow without chemical change, due to electron flow.
- Electrolytic: Electrical flow with chemical change, due to ion movement. Conduction increases with temperature increase.
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Types of Electrolytes:
- Strong Electrolytes: Completely dissociate into ions in solution (e.g., NaCl, HNO3).
- Weak Electrolytes: Incompletely dissociate into ions in solution, existing in equilibrium with their unionized molecules (e.g., CH3COOH, NH4OH).
Structure of Electrical Double Layer
- Electrical Double Layer (EDL): A structure formed at the electrode-electrolyte interface, involving ion distribution near the metal surface.
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Formation Cases:
- Case 1: Metal immersed in a solution containing its ions (e.g., Ag/AgNO₃). EDL structure depends on chemical potential differences. -If metal potential > solution potential, oxidation occurs, metal dissolves, and attracts oppositely charged ions from solution. -If metal potential < solution potential, reduction occurs, attracts metal ions from the solution to the metal surface, and oppositely charged ions from the solution.
- Case 2 (applied potential): Involves a specific potential, such as mercury with deaerated KCl to avoid electrochemical reaction. Ions are electrostatically attracted (or repelled) from the electrode.
- Case 3: No initial charge on the metal surface. Some ions specifically adsorb on the metal's surface via Vander Waals or covalent forces, creating the EDL.
Charge Transfer & Electrode Kinetics
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Reversible vs. Irreversible Processes:
- Reversible: Equilibrium, rate of oxidation = rate of reduction.
- Irreversible: Non-equilibrium, deviation from reversible potential. The difference is quantified by overpotential.
- Overpotential (η): Difference between irreversible (operating) and reversible potential. A measure of deviation from ideal behavior.
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Types of Overpotential:
- Ohmic (or Resistance): Due to resistance to current flow in the cell, from an oxide film or other obstacles. Minimized with strong electrolytes at high concentration.
- Concentration: Occurs when reaction rate is faster than the transport of reacting species to or from the electrode surface, resulting in a concentration difference.
- Activation: Due to energy barrier, needs to be overcome for reactants or intermediates to reach the transition state.
- Decomposition Potential: The minimum voltage required for continuous electrolysis.
Theories of Ionization and Electrolytic Conductance
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Arrhenius Theory: Suggests that electrolytes dissociate into ions, enabling electrical conduction. Limitations include the failure to account for ion-ion interactions (especially in strong electrolytes), and limitations in explaining the behavior of ionic strength.
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Ostwald's Dilution Law: Relates the equivalent conductance (Λc) to the degree of ionization (α) for a weak electrolyte, and how that changes with dilution of the electrolyte solution.
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Kohlrausch's Law: States that limiting equivalent conductivity of an electrolyte at infinite dilution is the sum of the limiting ionic conductances of its constituent ions.
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Debye-Huckel Theory: Provides a more accurate theoretical model, and accounts for the effect of interionic forces on ion behavior in solution, especially at higher concentrations than the limiting law.
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Ionic Strength (I): A measure of the total ion concentration in solution, which is important because ions with electrical charges affect each other, creating interactions that are reflected in the actual behavior of the electrolyte.
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Activity Coefficient: Accounts for the departure of electrolytic solutions from ideal behavior, due to interactions between ions.
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Capacity of EDL: The ability of the electrified double layer to store charge.
Additional Notes
- Diagrams and figures referenced in the text are not included in this summary.
- Concepts regarding specific conductance and molar and equivalent conductivity are not included, as they are subtopics within the larger concepts covered, and are not independently needed in all areas.
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Description
Test your knowledge on factors affecting ionic conductance in electrochemistry. This quiz covers topics such as the influence of ion size, solvent viscosity, and dielectric constants on conductance. Additionally, it delves into the behavior of electrolytes and current-potential curves during electrolysis.
