Chemistry
Electrolytes
Electrolytes are substances that conduct electricity when dissolved in water or melted. They are made up of ions, which are electrically charged particles. In solution, electrolytes can carry an electric current, making them essential for various biological and chemical processes, including nerve signaling and muscle contractions.
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8 Key excerpts on "Electrolytes"
eBook - PDF- Robert DeHoff(Author)
- 2006(Publication Date)
- CRC Press(Publisher)
The subset of science that deals with phenomena that combine chemical and electrical effects, electrochemistry, is exceedingly broad. 1–3 In this introductory text the focus is limited to the description of the conditions for equilibrium in such systems and applications derived from these conditions. The ionization energy of an element is the difference in energy between an atom of that element in its vapor state and an ion of the same element. When that element is present as a component in a solution its ionization energy may be greatly reduced as a result of its interactions with the surrounding solvent molecules. A salt dis-solved in water dissociates to a greater or lesser extent to form cations and anions. The resulting solution is called an electrolyte because it is found that a current of charge is transported through the solution by the ions when it is subject to an electric field. 1 1 The term electrolyte is also used to describe the compound that forms ions in solution. NaCl is an electrolyte; a solution of NaCl in water is also called an electrolyte. 523 Water is the most familiar and important solvent for Electrolytes; life itself depends upon this property of water. However, many other so-called polar solvents, such as acetone or glycerol, also form electrolyte solutions. Solid Electrolytes, in which a charge current is carried by diffusion of the ions in the system, also exist and find useful applications. The conditions for equilibrium in an electrolyte solution are derived in Section 15.1. In addition to the intensive properties dealt with in earlier chapters, every phase has an internal electric potential. If no external electrostatic field is applied, this potential is uniform within the phase at equilibrium. In considering the equilibrium between phases, it is not necessary to consider their differing electric potentials unless charged particles are transferred between the phases in the process being considered.
eBook - ePubPhysical Chemistry
How Chemistry Works
- Kurt W. Kolasinski(Author)
- 2016(Publication Date)
- Wiley(Publisher)
CHAPTER 14 Solutions of ElectrolytesPREVIEW OF IMPORTANT CONCEPTS
- Electrolytes dissolve in a solvent to produce solvated ions capable of conducting electricity.
- Strong Electrolytes dissolve almost completely into ions.
- Weak Electrolytes remain mostly in the molecular form.
- The solubility of an electrolyte is determined by the balance between the energy gained by holding the ions in a crystalline lattice as compared to the energy gained by solvating the ions in solution.
- In the limit of infinite dilution, all Electrolytes dissociate completely into ions.
- Ions in solution are surrounded by solvation shells. The first shell is fairly well ordered with a characteristic number of solvent molecules.
- The number of molecules in the first solvation shell is called the solvation number. It ranges from about 4 to 12 for simple ions. A value of 6 is quite common for aqueous transition metal cations.
- The most commonly used scale to describe the enthalpy and Gibbs energy of formation and absolute entropy of ions in aqueous solution is relative to the H+ . For H+ each of these three values is set equal to zero.
- Wallace Brey(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Five Solutions of Electrolytes Aqueous solutions of materials such as potassium chloride, sodium hydroxide, hydrochloric acid, magnesium sulfate, sodium acetate, tetramethylammonium bromide, or acetic acid are capable of con-ducting an electric current to a degree far surpassing the ability of pure water or of an aqueous solution of ethyl alcohol, sucrose, or acetone. Those materials that dissolve to yield a conducting solution—chiefly acids, bases, and salts—are called Electrolytes. Since an electric cur-rent can be carried only by the motion of electric charges, charged particles must be present in the solution of an electrolyte. These are the ions, positive and negative, comprising the solute before it dissolves, or formed from the interaction of the solvent and the solute. In this chapter, several methods of studying solutions of Electrolytes are described, and the models that have been developed to represent the behavior of ions in solution are discussed, with particular empha-sis on the effects of the relatively strong electrostatic forces between ions. 5-1 STRONG AND WEAK Electrolytes COLLIGATIVE PROPERTIES Some insight into the nature of solutions of Electrolytes can be ob-tained from measurements of their colligative properties. F o t example, the freezing point depression values for 0.1, 0.01, and 0.001 m solutions of sodium chloride in water are 0.346, 0.0361, and 0.00366°, respec-tively. Results of this sort are most informative if expressed as the ratio of the colligative property observed to the normal value expected for a nonelectrolyte of the same molal concentration, a ratio termed the van't Hoff factor and represented by the symbol i. For the three solutions, taken in order, the normal values of the freezing point de-pression are 0.186, 0.0186, and 0.00186°, so that i is 1.86, 1.94, and 1.97,
eBook - ePub- Cynthia G. Zoski(Author)
- 2006(Publication Date)
- Elsevier Science(Publisher)
3Solvents and Supporting Electrolytes
Stephen Creager, Department of Chemistry, Clemson University, Clemson, SC 29634, USAPublisher Summary
The chapter focuses on the properties of some solvent electrolyte combinations that are commonly used in electrochemical science. All electrochemical reactions and phenomena occur in a medium, usually a solvent containing dissolved ions that are mobile and able to support current flow. The properties of this medium are very important to any electrochemical experiment. One of the most important qualities that a medium possesses to be useful in electrochemical science is an ability to support current flow. Electrochemical reactions always produce or consume ions at electrodes. But the electrolyte provides the pathway for ions to flow between and among electrodes in the cell to maintain charge balance. Ionic conductivity in Electrolytes depends on two main factors: the concentration of free charge carriers and the ability of the charge carriers to move in an electric field. Electrolytes can be broadly considered in two groups: strong Electrolytes and weak Electrolytes. Strong Electrolytes are normally fully dissociated into ions when dissolved, whereas weak Electrolytes normally exist in a partially dissociated form such that some portion of the dissolved electrolyte exists in an uncharged form, usually a neutral molecule.3.1 INTRODUCTION
All electrochemical reactions and phenomena occur in a medium, usually a solvent containing dissolved ions (often called the supporting electrolyte or just the electrolyte) which are mobile and able to support current flow. The properties of this medium (which we will call the solvent-electrolyte combination, or sometimes the electrolyte for short) are critically important to any electrochemical experiment. A medium containing mobile ions must exist between the electrodes in an electrochemical cell to allow for control and/or measurement of the electrode potential in the cell, which is required in nearly all electrochemical experiments. A medium with good solvating power is needed to dissolve reactants and products from the electrode reaction, and one with reasonably low viscosity is often needed to allow for rapid transport of reactants and products to and from electrodes. Finally, a medium with low reactivity, or at least with a specific desired reactivity, is needed that will be compatible with oxidizing and reducing electrodes and with reactive species which might be created at electrodes, for any of a wide variety of reasons including analysis, synthesis, energy conversion, or simply the novelty of making a new species for the first time and studying its properties.
eBook - ePubEnergy Materials
A Short Introduction to Functional Materials for Energy Conversion and Storage
- Aliaksandr S. Bandarenka(Author)
- 2022(Publication Date)
- CRC Press(Publisher)
CHAPTER 4 Ionic ConductorsDOI: 10.1201/9781003025498-44.1 Electrolytes and Some Differences between Liquid and Solid Ion Conductors
As it was mentioned in previous sections, many energy conversion and storage devices deal with spontaneous spatially separated redox processes. The latter generally require suitable ionic conductors. Naturally, the performance of these devices depends on the properties of the electrode surface, the electrode/electrolyte interface, and of course, the properties of the Electrolytes. Liquid and solid ionic conductors are among the most important energy materials.Definition:
Electrolytes are usually liquids or solids, which conduct electricity through the movement of ions. Ionic conductivity is mutually connected with ion transport under the influence of an external electric field.There are several properties, which are fundamentally different in the case of electronic and ionic conductors. Among them are the specific conductivity values and their dependencies on temperature (see Table 4.1 ).One can arbitrarily distinguish at least three types of ionic conductors: inorganic solid, liquid, and polymer Electrolytes. The mechanism of conductivity and the area of applications of these materials are drastically different. Therefore, it is essential to understand what determines the ionic conductivity of solids and liquids, how the nature of electrolyte components influences their functionality, and what the design principles to construct such functional materials are.
eBook - ePub- Stéphane Leduc(Author)
- 2010(Publication Date)
- Perlego(Publisher)
On the other hand, if from a consideration of its freezing point and other constants we find that an electrolytic solution appears to contain n′ gramme-molecules per litre, the real number of chemical gramme-molecules in one litre of the solution will be only n′ / i = n. Very concentrated solutions do not conform to these laws. In this they resemble gases, which as they approach their point of condensation tend less and less to conform to the laws of gaseous pressure. Electrolysis. —If we take a solution of an acid, a salt, or a base, and dip into it two metallic rods, one connected to the positive and the other to the negative pole of a battery, we find that the metals or metallic radicals of the solution are liberated at the negative pole, while the acid radicals of the salts and acids and the hydroxyl of the bases are liberated at the positive pole. The liberated substances may either be discharged unchanged, or they may enter into new combinations, causing a series of secondary reactions. Electrolytes. —Solutions which conduct electricity are called Electrolytes, and the conducting metallic rods dipping into the solution are the Electrodes. Faraday gave the names of Ions to the atoms or atom-groups liberated at either electrode. The ions liberated at the positive electrode are the Anions, and those at the negative electrode are the Cations. The only solutions which possess any notable degree of electrical conductivity are the aqueous solutions of the various salts, acids, and bases, and in these solutions only do we meet with those phenomena of dissociation which are evidenced by anomalies of osmotic pressure, freezing point and the like,—anomalies which show that the solution contains a greater number of molecules than that indicated by its molecular concentration
eBook - ePubAspen Plus
Chemical Engineering Applications
- Kamal I. M. Al-Malah(Author)
- 2022(Publication Date)
- Wiley(Publisher)
11 ElectrolytesPROBLEM DESCRIPTION: WATER DE‐SOURING
A sour water stream, which contains 0.20 wt. % CO2 , 0.15 wt. % H2 S, and 0.1 wt. % NH3 at a temperature of 85°C and pressure of 1 atm with a mass flow rate of 5000 kg/hr, is to be treated by a dry steam at 1.1 atm and a mass flow rate of 1500 kg/hr. The water polluting compounds will be stripped off the sour water and vented, with some amount of water vapor, off the top of the stripping tower. The sweet water will be withdrawn from the bottom of the stripper with almost null of carbon, nitrogen, and sulfur content. The dry stream, entering from the bottom, will act as the vapor stream within the column; hence, no need for a reboiler. On the other end, the rising vapor stream will be substantially condensed and recycled to the top of the column as a liquid reflux, whereas the rest of it will be vented off the top of the tower.WHAT IS AN ELECTROLYTE?
In general, an electrolyte system is made of chemical species that can dissociate partially or totally into ions in a polar liquid medium (i.e., solvent). The liquid‐phase reaction always exists at its chemical equilibrium condition between the associate (i.e., condensed state) and dissociate (i.e., loose or ionic) form. The presence of ions in the liquid phase requires nonideal solution thermodynamics, where the activity coefficient, in general, is not unity. Some examples of Electrolytes are solutions of acids, bases, or salts, sour water solutions, aqueous amines, and hot carbonates. An electrolytic component can be classified under one of the following categories:- Solvent: The polar medium. Examples are: Water, methanol, ethanol, and acetic acid.
- Soluble Gas: A non‐condensable gas where its gas–liquid equilibrium (alternatively, its solubility in the given solvent) is described by Henry's Law. Examples are N2 , O2 , Cl2 , NH3 , and CO2 .
- Ion: an ionic (cationic or anionic) moiety with a formal charge. Examples are H3 O+ , OH− , Cl− , Na+ , HCO3− , CO3−2 , Ca+2 , Fe+2 , and Fe+3
eBook - ePub- Hailiang Wang, Boniface P. T. Fokwa, Hailiang Wang, Boniface P. T. Fokwa(Authors)
- 2019(Publication Date)
- Wiley(Publisher)
2 batteries are addressed.2 Ionic Conductivities and Lithium (Sodium) Transference Numbers
In the quest for finding a suitable electrolyte for battery technologies, one of the most relevant parameters to consider is the ionic conductivity. In soft matter, the ionic conductivity is proportional to the concentration of all ionic species c, their charge z, and mobility u:1The problem of improvement of the ionic conductivity in soft matter is nontrivial, as it is often so that the increase in the number of available ionic species leads to the increase in shear viscosity , and thus decrease of u. In addition, concentration of ionic species frequently cannot be increased by the simple increase of the total salt concentration csalt , since then neutral nonconductive species may form.Ionic conductivity is commonly determined by ac electrochemical impedance spectroscopy (EIS ) in a symmetrical cell with blocking electrodes such as stainless steel following the Ohm's law for the steady state conditions:2where l is the thickness of a thin electrolyte layer, Rb is the bulk electrolyte resistance, and A is the interfacial surface area.In many cases, soft matter Electrolytes display empirically determined exponential Vogel–Fulcher–Tamman dependency of ionic conductivity vs temperature:3where A and B are constants and T0 is the reference temperature (typically related to the glass transition temperature). Deviations of the VFT behavior due to the nonlinearity of the molecular volume vs T
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