This document discusses electric polarizability dispersion of alumina particles with adsorbed carboxymethyl cellulose. There is debate in the literature about whether condensed counterions along polymer chains are mobile or immobile when an electric field is applied. This experimental study uses electric light scattering to investigate an aqueous suspension of alumina particles with adsorbed carboxymethyl cellulose at different polyelectrolyte concentrations. The results indicate no additional polarizability component from condensed counterions, suggesting they are immobile in a sinusoidal electric field of moderate intensity from 10 Hz to 1 MHz.
Juornal of Physics Condensed Matter - Article IRossen Hristov
This document summarizes a study that investigated the mobility of counterions condensed on carboxymethyl cellulose (CMC) polymer chains adsorbed onto alumina colloid particles. Previous studies using electro-optical techniques reported that condensed counterions are mobile in alternating electric fields. However, the current study uses an amplitude approach, measuring particle polarizability at increasing CMC concentration rather than frequency dependence. Results indicate condensed counterions do not contribute to particle polarization at 1 kHz, suggesting they are immobile in sinusoidal fields up to 0.5 kV/cm and 1 kHz. Comparison of polarizability and electrophoretic mobility supports the conclusion that condensed counterions are immobilized on the CMC chains.
1. Electrochemistry deals with the production of electricity from chemical reactions and use of electricity to cause non-spontaneous reactions.
2. Conductors are classified as metallic conductors which allow current by electron movement and electrolytic conductors which allow current through dissolved or molten state with chemical decomposition.
3. Electrolytes are classified as strong which completely dissociate and weak which partially dissociate. Conductivity is directly proportional to concentration and inversely proportional to length.
Conductance is an ability of a material to allow the passage of current or fluid or temperature through different materials. It is opposite of resistance through a path, higher the conductivity of material lower is its resistance. It is most commonly used with electrical circuits, though it is also used in fluid and thermals. Copy the link given below and paste it in new browser window to get more information on Conductance:-
http://www.transtutors.com/homework-help/electrical-engineering/conductance.aspx
This document discusses the influence of various factors on counterion condensation in aqueous solutions of sodium polystyrenesulfonate polyelectrolyte. Electrical conductivity measurements were used to analyze the interactions between the polyion and counterions. The extent of counterion condensation was found to be affected by the polyelectrolyte concentration and molecular weight, added electrolyte concentration, and temperature. The results provide insight into how polyelectrolyte molecular weight influences counterion condensation behavior in the presence of added electrolytes.
Dynamic Stereochemistry and What role does conformation plays on stereochemistry is being exemplified in this presentation. Useful for the Undergraduate and Postgraduates students of Pharmacy, Pharmaceutical Chemistry and Chemical Sciences
1. The document discusses experimental methods to verify the validity of the Debye-Hückel and Onsager equations, which describe electrolyte behavior at high dilutions.
2. Using liquid membrane cells, studies were able to examine dilutions as high as 10-4 M and found that the Debye-Hückel equation holds for 1:1 electrolytes but shows negative deviations for 2:2 or 3:2 electrolytes.
3. Conductance measurements of various electrolytes at different temperatures found close agreement with the Onsager equation at low concentrations, validating it as accurately describing conductance behavior at high dilutions.
This document provides an introduction to conductometric titrations. It explains that conductometric titrations measure the change in conductivity at the endpoint of a titration reaction. The document discusses the principles behind conductivity changes during titrations and the apparatus used. It then describes the procedure for conductometric titrations and plots the results. Finally, it provides examples of different types of conductometric titrations including neutralization, redox, and precipitation titrations.
Juornal of Physics Condensed Matter - Article IRossen Hristov
This document summarizes a study that investigated the mobility of counterions condensed on carboxymethyl cellulose (CMC) polymer chains adsorbed onto alumina colloid particles. Previous studies using electro-optical techniques reported that condensed counterions are mobile in alternating electric fields. However, the current study uses an amplitude approach, measuring particle polarizability at increasing CMC concentration rather than frequency dependence. Results indicate condensed counterions do not contribute to particle polarization at 1 kHz, suggesting they are immobile in sinusoidal fields up to 0.5 kV/cm and 1 kHz. Comparison of polarizability and electrophoretic mobility supports the conclusion that condensed counterions are immobilized on the CMC chains.
1. Electrochemistry deals with the production of electricity from chemical reactions and use of electricity to cause non-spontaneous reactions.
2. Conductors are classified as metallic conductors which allow current by electron movement and electrolytic conductors which allow current through dissolved or molten state with chemical decomposition.
3. Electrolytes are classified as strong which completely dissociate and weak which partially dissociate. Conductivity is directly proportional to concentration and inversely proportional to length.
Conductance is an ability of a material to allow the passage of current or fluid or temperature through different materials. It is opposite of resistance through a path, higher the conductivity of material lower is its resistance. It is most commonly used with electrical circuits, though it is also used in fluid and thermals. Copy the link given below and paste it in new browser window to get more information on Conductance:-
http://www.transtutors.com/homework-help/electrical-engineering/conductance.aspx
This document discusses the influence of various factors on counterion condensation in aqueous solutions of sodium polystyrenesulfonate polyelectrolyte. Electrical conductivity measurements were used to analyze the interactions between the polyion and counterions. The extent of counterion condensation was found to be affected by the polyelectrolyte concentration and molecular weight, added electrolyte concentration, and temperature. The results provide insight into how polyelectrolyte molecular weight influences counterion condensation behavior in the presence of added electrolytes.
Dynamic Stereochemistry and What role does conformation plays on stereochemistry is being exemplified in this presentation. Useful for the Undergraduate and Postgraduates students of Pharmacy, Pharmaceutical Chemistry and Chemical Sciences
1. The document discusses experimental methods to verify the validity of the Debye-Hückel and Onsager equations, which describe electrolyte behavior at high dilutions.
2. Using liquid membrane cells, studies were able to examine dilutions as high as 10-4 M and found that the Debye-Hückel equation holds for 1:1 electrolytes but shows negative deviations for 2:2 or 3:2 electrolytes.
3. Conductance measurements of various electrolytes at different temperatures found close agreement with the Onsager equation at low concentrations, validating it as accurately describing conductance behavior at high dilutions.
This document provides an introduction to conductometric titrations. It explains that conductometric titrations measure the change in conductivity at the endpoint of a titration reaction. The document discusses the principles behind conductivity changes during titrations and the apparatus used. It then describes the procedure for conductometric titrations and plots the results. Finally, it provides examples of different types of conductometric titrations including neutralization, redox, and precipitation titrations.
Molecular dynamics-of-ions-in-two-forms-of-an-electroactive-polymerDarren Martin Leith
This document summarizes molecular dynamics simulations of two forms of an electroactive polymer interacting with ions. In one simulation, an amphiphilic polymer forms a charged monolayer interface between a vacuum and an aqueous layer containing ions. The stability of the monolayer under hydrostatic pressure and charge imbalance is investigated. In another simulation, a polythiophene oligomer is twisted into a helix serving as an ion channel between two aqueous regions separated by a phospholipid bilayer membrane.
This document summarizes an experiment investigating the behavior of a single fuel cell under different membrane electrode assemblies (MEAs) and fuels. Three MEAs using different catalysts were tested with hydrogen and formic acid as anode fuels and hydrogen, air, or water as cathode reactants. Constant base current with 10A pulses were applied to alleviate carbon monoxide poisoning on the anode. Results including polarization curves and potential/current oscillations are presented. The document also provides background on fuel cells and mechanisms of carbon monoxide poisoning.
This document discusses conductometry, which is a method of analysis based on measuring the electrolytic conductance of a solution. It begins by classifying different electrochemical methods, including conductometry and electrophoresis which do not involve redox reactions. It then discusses key concepts in conductometry such as conductivity, conductance, equivalent conductance, and how various factors like ion nature, temperature, concentration, and electrode size affect conductance. It also provides examples of calculating conductance and equivalent conductance from experimental measurements. Instrumentation for conductometric determination includes a conductance cell and conductivity bridge.
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
Physical Chemistry
This document contains notes on physical chemistry unit 3 covering topics like conductance, equivalent and molar conductivity, Kohlrausch law, transport numbers and their experimental determination using Hittorf and moving boundary methods. It also discusses applications of conductance measurements like determination of degree of ionization of weak electrolytes, solubility of sparingly soluble salts, ionic product of water, and conductometric titrations.
1) Electrogenic pumps like the Na+/K+ ATPase transport ions across membranes using energy from ATP hydrolysis. This leads to a net movement of charge across the membrane.
2) Early models assumed passive ion diffusion established ion gradients, but problems arose. Equations were developed but inconsistencies emerged when applying them to plant cells.
3) The mechanism of the Na+/K+ ATPase involves ions binding deep within the protein and moving through access channels to binding sites. Transient currents from external ions like K+ and Na+ moving through these channels have been measured.
Ion mobility spectrometry (IMS) is an analytical technique used to detect explosives and other chemicals. It works by ionizing vapor samples, separating the ions based on their mobility in an electric field, and detecting the ions. IMS provides fast, sensitive detection and is used in security applications like airports and public events. The document discusses the principles and components of IMS, including ionization methods, ion separation techniques, and factors that determine the resolution, sensitivity and detection limits of IMS systems. Commercial applications of IMS are highlighted, such as explosive detectors, air quality monitors, and portals used to screen people for explosive residues.
Introduction
working principle
fragmentation process
general rules for fragmentation
general modes of fragmentation
metastable ions
isotopic peaks
applications
This document provides an overview of conductometry. It discusses how conductometry measures the conductance of electrolyte solutions using a conductivity cell and conductometer. It describes different types of conductivity cells and how conductometric titrations work by measuring changes in conductance during titrations. Examples of various acid-base titrations are given. Conductometric titrations can be used to analyze many different samples and have advantages like not requiring indicators. Applications include measuring water pollution, food analyses, and more.
This document discusses electrochemical methods and conductometry. It introduces conductometry as the determination of electrical conductance of an electrolyte solution using a conductometer. Conductometry is based on how ions in solution affect conductivity, which depends on ion type, concentration, temperature and mobility. The principles of conductometry and conductometric titration are explained. Conductometric titration involves substituting ions of one mobility for ions of another mobility until the equivalence point is reached. Examples of different types of titrations such as strong acid-strong base, strong acid-weak base, weak acid-strong base, and weak acid-weak base are provided.
This document provides an overview of conductometry and its applications. It discusses Ohm's law and how conductivity is measured using electrodes, standard solutions, and a conductivity cell. Factors that affect conductivity include ion size, temperature, charge, and number. Conductometric titrations can be used to determine endpoints and are advantageous because no indicator is needed. Types of titrations discussed include acid-base, precipitation, replacement, redox, and complexometric. Recent applications include use in refineries, estimating polyelectrolytes, and biotechnology/environmental monitoring.
1) Three major factors that increase the conductance of strong electrolytes are the relaxation effect, electrophoretic effect, and frictional resistance of the medium.
2) The relaxation effect occurs when an ion moves and has to rebuild its ionic atmosphere around it, slowing its motion. The electrophoretic effect occurs when ions move against the stream of oppositely charged solvent molecules in their ionic atmosphere.
3) The Debye-Hückel-Onsager equation mathematically relates equivalent conductance to concentration, taking into account these factors. It indicates equivalent conductance decreases with increasing concentration.
Conductometric analysis measures the electrical conductivity of solutions to determine analyte concentration. It works by measuring how easily ions move through the solution when a current is applied. There are several types of conductometric titrations including acid-base, redox, and complexometric titrations. Conductometric titrations can determine the endpoint graphically without needing indicators and work well for colored, weak, or turbid solutions. The conductivity is measured using a conductometer with conductivity cells and platinum electrodes to apply a current and measure the solution's resistance.
Determination of equivalence conductance, degree of dissociation and dissocia...Mithil Fal Desai
1) This document outlines a procedure to determine the equivalence conductance, degree of dissociation, and dissociation constant of acetic acid, a weak acid.
2) The experiment involves measuring the conductance of acetic acid solutions at different concentrations and using equations relating conductance, concentration, and degree of dissociation.
3) Key results include the equivalence conductance and degree of dissociation of 0.1N acetic acid, as well as the dissociation constant determined graphically from a plot of (α2/(1-α)) vs. 1/concentration.
This document reviews the polarization resistance method for determining instantaneous corrosion rates of metals. It discusses how polarization resistance (Rp) is derived from electrode kinetics equations and relates Rp to corrosion current density and rate. A variety of time domain electrochemical methods can be used to experimentally determine Rp, including potential step, current step, and potentiodynamic techniques. Factors that can complicate accurate measurement of Rp are also examined, such as diffusion effects, film formation, and non-uniform current/potential distributions.
The Brønsted catalysis relationship is a Linear Free Energy Relationship (LFER) that relates ionization of an acid or base which catalyzes a reaction and the rate of the reaction.
Contributed by: Quincy Davis, Jonathan Greenhalgh, Joshua Visser (Undergraduates), University of Utah, 2016
Determination of the hydrogen coefficient diffusion DH in the MmNi3.55Mn0.4Al...AI Publications
The hydrogen storage alloys MmNi3.55Mn0.4Al0.3Co0.75-xFex (0 ≤ x ≤0.75) were used as negative electrodes in the Ni-MH accumulators. The chronopotentiommetry and the cyclic voltammetry were applied to characterize the electrochemical properties of these alloys. The obtained results showed that the substitution of the cobalt atoms by iron atoms has a good effect on the life cycle of the electrode. The discharge capacity reaches its maximum in MmNi3.55Mn0.4Al0.3Co0.75-x Fex ( x = 0, 0.15, 0.35, 0.55 and 0.75) are, respectively, equal to 270, 266, 260, 210 and 200 mAh/g after 12 charge-discharge cycles. The diffusion behaviour of hydrogen in the negative electrodes made from these alloys was characterized by cyclic voltammetry after few activation cycles. The values of the hydrogen coefficient in MmNi3.55Mn0.4Al0.3Co0.75-x Fex ( x = 0, 0.15, 0.35, 0.55 and 0.75) are, respectively, equal to 5.86 10-10, 1.95 10-9, 3.44 10-9, 2.96 10-9 and 4.98 10-10 cm2 s-1. However, the values of the charge transfer coefficients are respectively equal to 0.35, 0.6, 0.5, 0.33 and 0.3. These results showed that the substitution of cobalt by iron decreases the reversibility and the kinetic of the electrochemical reaction in these alloys.
It is an electrochemical method of analysis used for the determination or measurement of the electrical conductance of an electrolyte solution by means of a conductometer.
Electric conductivity of an electrolyte solution depends on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
The main principle involved in this method is that the movement of the ions creates the electrical conductivity. The movement of the ions is mainly depended on the concentration of the ions.
The electric conductance in accordance with ohms law which states that the strength of current (i) passing through conductor is directly proportional to potential difference & inversely to resistance.
i =V/R
lecture slide on:
Gibbs free energy and Nernst Equation, Faradaic Processes and Factors Affecting Rates of Electrode Reactions, Potentials and Thermodynamics of Cells, Kinetics of Electrode Reactions, Kinetic controlled reactions,Essentials of Electrode Reactions,BUTLER-VOLMER MODEL FOR THE ONE-STEP, ONE-ELECTRON PROCESS,Current-overpotential curves for the system, Mass Transfer by Migration And Diffusion,MASS-TRANSFER-CONTROLLED REACTIONS,
This document presents a theoretical model for simulating cyclic voltammetry experiments under conditions where migration effects are significant due to low supporting electrolyte concentrations. The model involves numerically solving the coupled Nernst-Planck and Poisson equations to determine concentration and potential profiles throughout the solution. Parameters such as electrode size, scan rate, diffusion coefficients, and supporting electrolyte concentration are varied to examine their effects on the voltammogram shape. Experimental cyclic voltammetry data for a ruthenium complex with varying amounts of KCl supporting electrolyte is also presented for comparison to the model. The model is shown to be applicable when the ratio of supporting electrolyte to analyte concentration exceeds 30.
Molecular dynamics-of-ions-in-two-forms-of-an-electroactive-polymerDarren Martin Leith
This document summarizes molecular dynamics simulations of two forms of an electroactive polymer interacting with ions. In one simulation, an amphiphilic polymer forms a charged monolayer interface between a vacuum and an aqueous layer containing ions. The stability of the monolayer under hydrostatic pressure and charge imbalance is investigated. In another simulation, a polythiophene oligomer is twisted into a helix serving as an ion channel between two aqueous regions separated by a phospholipid bilayer membrane.
This document summarizes an experiment investigating the behavior of a single fuel cell under different membrane electrode assemblies (MEAs) and fuels. Three MEAs using different catalysts were tested with hydrogen and formic acid as anode fuels and hydrogen, air, or water as cathode reactants. Constant base current with 10A pulses were applied to alleviate carbon monoxide poisoning on the anode. Results including polarization curves and potential/current oscillations are presented. The document also provides background on fuel cells and mechanisms of carbon monoxide poisoning.
This document discusses conductometry, which is a method of analysis based on measuring the electrolytic conductance of a solution. It begins by classifying different electrochemical methods, including conductometry and electrophoresis which do not involve redox reactions. It then discusses key concepts in conductometry such as conductivity, conductance, equivalent conductance, and how various factors like ion nature, temperature, concentration, and electrode size affect conductance. It also provides examples of calculating conductance and equivalent conductance from experimental measurements. Instrumentation for conductometric determination includes a conductance cell and conductivity bridge.
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
Physical Chemistry
This document contains notes on physical chemistry unit 3 covering topics like conductance, equivalent and molar conductivity, Kohlrausch law, transport numbers and their experimental determination using Hittorf and moving boundary methods. It also discusses applications of conductance measurements like determination of degree of ionization of weak electrolytes, solubility of sparingly soluble salts, ionic product of water, and conductometric titrations.
1) Electrogenic pumps like the Na+/K+ ATPase transport ions across membranes using energy from ATP hydrolysis. This leads to a net movement of charge across the membrane.
2) Early models assumed passive ion diffusion established ion gradients, but problems arose. Equations were developed but inconsistencies emerged when applying them to plant cells.
3) The mechanism of the Na+/K+ ATPase involves ions binding deep within the protein and moving through access channels to binding sites. Transient currents from external ions like K+ and Na+ moving through these channels have been measured.
Ion mobility spectrometry (IMS) is an analytical technique used to detect explosives and other chemicals. It works by ionizing vapor samples, separating the ions based on their mobility in an electric field, and detecting the ions. IMS provides fast, sensitive detection and is used in security applications like airports and public events. The document discusses the principles and components of IMS, including ionization methods, ion separation techniques, and factors that determine the resolution, sensitivity and detection limits of IMS systems. Commercial applications of IMS are highlighted, such as explosive detectors, air quality monitors, and portals used to screen people for explosive residues.
Introduction
working principle
fragmentation process
general rules for fragmentation
general modes of fragmentation
metastable ions
isotopic peaks
applications
This document provides an overview of conductometry. It discusses how conductometry measures the conductance of electrolyte solutions using a conductivity cell and conductometer. It describes different types of conductivity cells and how conductometric titrations work by measuring changes in conductance during titrations. Examples of various acid-base titrations are given. Conductometric titrations can be used to analyze many different samples and have advantages like not requiring indicators. Applications include measuring water pollution, food analyses, and more.
This document discusses electrochemical methods and conductometry. It introduces conductometry as the determination of electrical conductance of an electrolyte solution using a conductometer. Conductometry is based on how ions in solution affect conductivity, which depends on ion type, concentration, temperature and mobility. The principles of conductometry and conductometric titration are explained. Conductometric titration involves substituting ions of one mobility for ions of another mobility until the equivalence point is reached. Examples of different types of titrations such as strong acid-strong base, strong acid-weak base, weak acid-strong base, and weak acid-weak base are provided.
This document provides an overview of conductometry and its applications. It discusses Ohm's law and how conductivity is measured using electrodes, standard solutions, and a conductivity cell. Factors that affect conductivity include ion size, temperature, charge, and number. Conductometric titrations can be used to determine endpoints and are advantageous because no indicator is needed. Types of titrations discussed include acid-base, precipitation, replacement, redox, and complexometric. Recent applications include use in refineries, estimating polyelectrolytes, and biotechnology/environmental monitoring.
1) Three major factors that increase the conductance of strong electrolytes are the relaxation effect, electrophoretic effect, and frictional resistance of the medium.
2) The relaxation effect occurs when an ion moves and has to rebuild its ionic atmosphere around it, slowing its motion. The electrophoretic effect occurs when ions move against the stream of oppositely charged solvent molecules in their ionic atmosphere.
3) The Debye-Hückel-Onsager equation mathematically relates equivalent conductance to concentration, taking into account these factors. It indicates equivalent conductance decreases with increasing concentration.
Conductometric analysis measures the electrical conductivity of solutions to determine analyte concentration. It works by measuring how easily ions move through the solution when a current is applied. There are several types of conductometric titrations including acid-base, redox, and complexometric titrations. Conductometric titrations can determine the endpoint graphically without needing indicators and work well for colored, weak, or turbid solutions. The conductivity is measured using a conductometer with conductivity cells and platinum electrodes to apply a current and measure the solution's resistance.
Determination of equivalence conductance, degree of dissociation and dissocia...Mithil Fal Desai
1) This document outlines a procedure to determine the equivalence conductance, degree of dissociation, and dissociation constant of acetic acid, a weak acid.
2) The experiment involves measuring the conductance of acetic acid solutions at different concentrations and using equations relating conductance, concentration, and degree of dissociation.
3) Key results include the equivalence conductance and degree of dissociation of 0.1N acetic acid, as well as the dissociation constant determined graphically from a plot of (α2/(1-α)) vs. 1/concentration.
This document reviews the polarization resistance method for determining instantaneous corrosion rates of metals. It discusses how polarization resistance (Rp) is derived from electrode kinetics equations and relates Rp to corrosion current density and rate. A variety of time domain electrochemical methods can be used to experimentally determine Rp, including potential step, current step, and potentiodynamic techniques. Factors that can complicate accurate measurement of Rp are also examined, such as diffusion effects, film formation, and non-uniform current/potential distributions.
The Brønsted catalysis relationship is a Linear Free Energy Relationship (LFER) that relates ionization of an acid or base which catalyzes a reaction and the rate of the reaction.
Contributed by: Quincy Davis, Jonathan Greenhalgh, Joshua Visser (Undergraduates), University of Utah, 2016
Determination of the hydrogen coefficient diffusion DH in the MmNi3.55Mn0.4Al...AI Publications
The hydrogen storage alloys MmNi3.55Mn0.4Al0.3Co0.75-xFex (0 ≤ x ≤0.75) were used as negative electrodes in the Ni-MH accumulators. The chronopotentiommetry and the cyclic voltammetry were applied to characterize the electrochemical properties of these alloys. The obtained results showed that the substitution of the cobalt atoms by iron atoms has a good effect on the life cycle of the electrode. The discharge capacity reaches its maximum in MmNi3.55Mn0.4Al0.3Co0.75-x Fex ( x = 0, 0.15, 0.35, 0.55 and 0.75) are, respectively, equal to 270, 266, 260, 210 and 200 mAh/g after 12 charge-discharge cycles. The diffusion behaviour of hydrogen in the negative electrodes made from these alloys was characterized by cyclic voltammetry after few activation cycles. The values of the hydrogen coefficient in MmNi3.55Mn0.4Al0.3Co0.75-x Fex ( x = 0, 0.15, 0.35, 0.55 and 0.75) are, respectively, equal to 5.86 10-10, 1.95 10-9, 3.44 10-9, 2.96 10-9 and 4.98 10-10 cm2 s-1. However, the values of the charge transfer coefficients are respectively equal to 0.35, 0.6, 0.5, 0.33 and 0.3. These results showed that the substitution of cobalt by iron decreases the reversibility and the kinetic of the electrochemical reaction in these alloys.
It is an electrochemical method of analysis used for the determination or measurement of the electrical conductance of an electrolyte solution by means of a conductometer.
Electric conductivity of an electrolyte solution depends on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
The main principle involved in this method is that the movement of the ions creates the electrical conductivity. The movement of the ions is mainly depended on the concentration of the ions.
The electric conductance in accordance with ohms law which states that the strength of current (i) passing through conductor is directly proportional to potential difference & inversely to resistance.
i =V/R
lecture slide on:
Gibbs free energy and Nernst Equation, Faradaic Processes and Factors Affecting Rates of Electrode Reactions, Potentials and Thermodynamics of Cells, Kinetics of Electrode Reactions, Kinetic controlled reactions,Essentials of Electrode Reactions,BUTLER-VOLMER MODEL FOR THE ONE-STEP, ONE-ELECTRON PROCESS,Current-overpotential curves for the system, Mass Transfer by Migration And Diffusion,MASS-TRANSFER-CONTROLLED REACTIONS,
This document presents a theoretical model for simulating cyclic voltammetry experiments under conditions where migration effects are significant due to low supporting electrolyte concentrations. The model involves numerically solving the coupled Nernst-Planck and Poisson equations to determine concentration and potential profiles throughout the solution. Parameters such as electrode size, scan rate, diffusion coefficients, and supporting electrolyte concentration are varied to examine their effects on the voltammogram shape. Experimental cyclic voltammetry data for a ruthenium complex with varying amounts of KCl supporting electrolyte is also presented for comparison to the model. The model is shown to be applicable when the ratio of supporting electrolyte to analyte concentration exceeds 30.
The document discusses a study that measured the electrical conductivity of solutions of sodium polystyrenesulphonate in mixed solvent systems of 2-ethoxyethanol and water at varying concentrations, temperatures, and solvent compositions. The results showed that equivalent conductivity increased slightly with decreasing polymer concentration. Equivalent conductivity also increased with increasing temperature and relative permittivity of the solvent system. However, the experimentally determined conductivities did not fully match what was predicted by Manning's counterion condensation theory. Reasons for this discrepancy are discussed.
This document discusses the adsorption of carboxymethyl cellulose (CMC) onto alumina particles. CMC and alumina were chosen because their surface charges can be altered by pH, allowing the study of particle aggregation and stabilization. Electric light scattering and microelectrophoresis techniques were used to measure how CMC adsorption affects the electric polarizability and surface charge of the alumina particles over time and across a range of CMC concentrations. The results provide conditions for complete CMC adsorption and suspension stability.
This document provides an overview of semiconductor theory and band theory of solids. It discusses how band theory can explain the differing electrical properties of conductors, semiconductors, and insulators based on their band structure and energy gaps. Semiconductors have a small energy gap between the valence and conduction bands that can be overcome by thermal excitation, allowing some electrons to reach the conduction band. Doping semiconductors with impurities can create n-type or p-type materials by introducing extra electrons or holes that increase conductivity. The document also covers thermoelectric effects in semiconductors.
The document discusses semiconductor theory and band theory of solids. It introduces band theory, which explains that in solids electron energy levels split into nearly continuous bands separated by forbidden gaps. Semiconductors have a small band gap (<1eV) allowing thermal excitation of electrons across the gap. This explains their decreasing resistivity with increasing temperature as electrons jump from the valence to conduction band. The Kronig-Penney model further illustrates band structure and forbidden gaps in semiconductors.
CBSE Class 12 Chemistry Chapter 3 (Electrochemistry) | Homi InstituteHomi Institute
1. Electrochemistry is the study of chemical processes involving the movement of electrons, which can generate electricity through oxidation-reduction reactions.
2. A salt bridge is a device used in electrochemical cells to connect the half cells and maintain electrical neutrality, preventing the accumulation of charges that would stop the reaction.
3. Common reference electrodes include the standard hydrogen electrode and silver-silver chloride electrode, but the standard hydrogen electrode is difficult to assemble and maintain precisely.
This document discusses band theory and semiconductor theory. It begins by introducing band theory, which models the allowed energy states in solids as continuous bands separated by forbidden gaps. Semiconductors are defined as having small band gaps (<1 eV), allowing thermal excitation of electrons across the gap. This explains their decreasing resistivity with increasing temperature. The Kronig-Penney model is presented to illustrate how periodic lattice potentials create energy bands and gaps. Semiconductors have filled valence bands separated from conduction bands by small gaps, whereas insulators have larger gaps preventing electrical conduction. Empirical models are discussed for describing the temperature dependence of resistivity in semiconductors.
The document summarizes research on generating and observing stable vortex lattices in polariton condensates in semiconductor microcavities. Researchers pumped three spots in a triangular geometry and observed the formation of a honeycomb lattice containing up to 100 vortices and antivortices extending over tens of microns. Numerical simulations matched the experimental observations and showed the lattice forms due to ferromagnetic coupling between the condensates at each pumped spot, with the phase locked by the imposed triangular geometry. The vortex lattice was stable for many minutes and highly sensitive to the optically imposed geometry.
This document outlines a graduate student's thesis work on multi-scale modeling of micro-coronas. There are wide variations in both time and length scales involved in plasma modeling, from picoseconds to hours/days and from molecular to macroscopic scales. A multi-scale modeling technique of domain decomposition is proposed, using microscopic models locally where needed and macroscopic models for the rest. The goals are to develop a modeling tool that can span micro- to macro-scales and simulate plasmas in complex geometries. Challenges include bridging between scales and incorporating particle and fluid models.
My_papers_Nastishin_PRL_2012_Elasticity of Lyotropic Chromonic Liquid Crystal...Myroslava Omelchenko
This document reports on a study that uses a magnetic Frederiks transition technique to measure the elastic constants (splay K1, twist K2, bend K3) of the lyotropic chromonic liquid crystal sunset yellow formed through reversible aggregation of organic molecules in water. The key findings are:
1) K1 and K3 are comparable in magnitude and about an order of magnitude higher than K2.
2) At higher concentrations and lower temperatures, K1 and the ratios K1/K3 and K1/K2 increase, which is attributed to elongation of the self-assembled lyotropic chromonic liquid crystal aggregates.
3) This concentration and temperature dependence of the elastic constants
This document discusses electrochemistry and key concepts related to conductivity of electrolyte solutions. It defines electrochemistry as the study of chemical reactions caused by electricity or electrical energy and the conversion between chemical and electrical energy. It describes how conductivity is measured and how it varies with concentration, temperature, and other factors for strong and weak electrolytes. The document also discusses concepts such as molar conductivity, transport numbers, solubility products, and the Debye-Hückel theory of ionic interactions.
Semiconductor theory describes how small amounts of impurities can be added to intrinsic semiconductors to create n-type and p-type materials. N-type semiconductors are created by adding elements with extra electrons, while p-type are created by adding elements with electron deficiencies. The junction between a p-type and n-type material allows current to flow in only one direction, forming the basis for important semiconductor devices such as diodes, transistors, and solar cells.
Transition in ultraviolet and visible lightMzgin Mohammed
The document discusses UV-Vis spectroscopy and factors that influence molar absorptivity. It describes the four types of electronic transitions (s-s*, n-s*, n-p*, p-p*) and explains that the p-p* transition is most useful for quantitative analysis due to its high absorptivity at moderate energies. Solvent polarity and conjugation affect transition energies and absorptivities. Chromophores like alkenes and aromatics absorb in the UV-Vis region. The document also discusses applications of UV-Vis spectroscopy for qualitative and quantitative analysis.
The document summarizes a study that investigated how the photoluminescence quantum yield of lead selenide quantum dots is affected by increasing excitation energy. Three samples of PbSe quantum dots were synthesized with different diameters and characterized. It was found that the quantum yield decreased as the excitation energy increased, likely due to the formation of multi-exciton states within single quantum dots that lead to non-radiative Auger processes. The quantum yield was measured using an integrating sphere method and by analyzing absorption and emission spectra of the samples excited at different wavelengths. The results supported the expectation that higher excitation energies reduce quantum yield.
This document provides an overview of semiconductor theory and devices. It begins by introducing the three categories of solids based on electrical conductivity: conductors, semiconductors, and insulators. It then discusses band theory, which models the allowed energy states in solids as continuous bands separated by forbidden gaps. Semiconductors are defined as having energy gaps small enough for thermal excitation of electrons between bands. The document covers models like the Kronig-Penney model that explain energy gaps. It also discusses how temperature affects resistivity in semiconductors by increasing the number of electrons excited into the conduction band.
This document provides an introduction to electroanalytical chemistry. It discusses electrochemical cells and cell potential, as well as current in electrochemical cells. The main types of electroanalytical methods are potentiometry, coulometry, and voltammetry. Electroanalytical techniques measure electrical properties like current, resistance, and voltage in solutions containing analytes. They can produce low detection limits and provide information about reaction stoichiometry, rates, and equilibrium constants. Mass transport of species to electrode surfaces can occur through diffusion, migration, or convection. Different types of currents and polarization effects are also discussed.
A molecular-dynamics-investigation-of-the-stability-of-a-charged-electroactiv...Darren Martin Leith
1) A molecular dynamics simulation investigates the stability of a charged electroactive polymer monolayer consisting of an amphiphilic polythiophene on a sodium chloride solution.
2) When the monolayer is chemically reduced, negative charges are conferred on the thiophene rings. This leads to a loss of planarity and buckling of the monolayer, eventually causing it to rupture. It also attracts excess sodium ions to the interface.
3) At low levels of reduction, interface sodium ions are more mobile than sodium ions in the NaCl solution, responding to electric fields by jumping between sites with an energy barrier of 0.33 eV. The instability of the charged polymer membrane is discussed using Gou
Dynamical symmetry breaking in vibration-assisted transport through nanostruc...Vorname Nachname
This document summarizes a theoretical model of electron transport through a nanostructure with strong electron-vibron coupling. A single molecule is coupled to many vibronic modes, and at low energies transport is dominated by electron-vibron processes where an electron transfers through the molecule accompanied by the excitation or emission of vibrons. When the vibron frequencies form a harmonic series, energetically degenerate vibronic configurations can contribute to transport. Both negative differential conductance features and gate asymmetry are predicted due to interplay between Franck-Condon suppression and spin/orbital degeneracies, which give rise to slow transport channels.
This document discusses the principles and procedures of conductometric analysis. Conductometric analysis measures the electrical conductivity of a solution due to ion mobility. The conductivity is affected by factors like number, charge, size of ions, and temperature. It involves titrating a solution containing ions and measuring the change in conductivity. This allows determination of the endpoint of the titration from the plotted conductivity-volume curve. The document defines key terms, describes instrumentation including conductivity cells and electrodes, and discusses different types of conductometric titrations like acid-base, redox, and complexometric titrations. Conductometric titrations provide accurate results for analyses without requiring indicators.
Similar to 2014-RSC-Advances_AZ-RH_CMC-Frequency (20)