Is O2 A Strong Electrolyte

Strong Electrolyte

CHEMICAL REACTIONS

Fifty.D. LANDAU , ... Due east.1000. LIFSHITZ , in General Physics, 1967

§90. Weak electrolytes

As well as potent electrolytes, in that location are substances which dissociate in solution but practice and then but partly; in solutions of these substances at that place are not only ions but too neutral molecules. Such substances are called weak electrolytes. The bulk of acids and bases, and some salts (such equally HgCl_two), are weak electrolytes in aqueous solution.

The police force of mass action is applicable to weak solutions of weak electrolytes. Allow us consider, for instance, a solution of acetic acid (CH₃COOH), which dissociates in water according to the equation

$\text{HAc}={\text{H}}^{+}+{\text{Ac}}^{-}$

(the symbol Ac cogent the acrid radical CH₃COO). Dissociation continues until equilibrium is established, when the ion concentrations satisfy the equation

$\left[{\text{Ac}}^{-}\right]\left[{\text{H}}^{\text{+}}\right]/\left[\text{HAc}\right]=\mathrm{Grand}.$

The constant K is chosen the dissociation constant. For case, for acetic acrid at room temperature K = 2 × 10^−five mole/litre.

A dissociation reaction is endothermic, i.e. it occurs with assimilation of heat. Every bit with all endothermic reactions, its "yield" increases with ascent temperature, i.e. the dissociation constant increases.

The dissociation abiding is independent of the quantity of dissolved electrolyte (and then long as the solution remains weak) and is a fundamental property of the electrolyte, but the degree of dissociation (i.due east. the ratio of the number of dissociated molecules to the total number of electrolyte molecules) depends on the concentration of the solution.

Allow a full of c moles of electrolyte exist dissolved in a litre of water, and let the degree of dissociation be α. So the number of dissociated moles is cα. If an electrolyte molecule dissociates into 1 anion and one cation (as in the example of acetic acid considered in a higher place), then the concentration of each is cα. The concentration of undissociated molecules is c(1 – α). The law of mass action therefore gives

${\alpha }^{2}c/\left(1-\alpha \right)=K.$

Hence we find the degree of dissociation in terms of the concentration of the solution:

$\alpha =\frac{-K+\sqrt{\left(K^{\mathrm{two}}+4Kc\right)}}{2c}=\frac{2k}{K+\sqrt{\left(K^2+4Kc\right)}}.$

This formula shows that, as the concentration c decreases, the degree of dissociation increases, tending to unity at space dilution (i.east. as c → 0). Thus, the more dilute the solution, the more the electrolyte is dissociated. This naturally follows from the fact that a molecule dissociates under the activeness of h2o molecules, which are present everywhere, but for recombination to occur two unlike ions must come together, and this occurs more rarely in more dilute solutions.

Water is itself a very weak electrolyte. A very minor fraction of its molecules are dissociated in accordance with the equation

${\text{H}}_2\text{O}={\text{H}}^{+}+{\text{OH}}^{-}.$

Since H_iiO is at the same time the solvent with respect to the ions H⁺ and OH⁻, the formula for the law of mass action demand include, as we know, but the concentrations of these ions:

$\left[{\text{H}}^{+}\right]\left[{\text{OH}}^{-}\right]=M.$

For pure water at 25°C,

$G={\mathrm{ten}}^{-\mathrm{xiv}}{\left(\text{mole/litre}\right)}^{\mathrm{two}}.$

Since in pure water the concentrations of H⁺ and OH⁻ ions are obviously equal, nosotros observe that each is 10^−vii. Thus one litre of water contains only 10⁻⁷ mole of H⁺ ions (and the same quantity of OH⁻); i mole of water (18 grand) is dissociated merely in 10 meg litres.

The decimal logarithm of the concentration of H⁺ ions, with sign reversed, is called the pH:

$\text{pH}=-{\log }_{10}\left[{\text{H}}^{+}\right].$

For pure water at 25°C the pH is 7·0; at 0°C it is seven·5 and at 60°C 6·v.

When acids dissolve they release H⁺ ions. But the product of concentrations [H⁺][OH⁻] must remain constant and equal to x⁻¹⁴. Some of the OH⁻ ions must therefore combine with H⁺ ions to form neutral molecules of water. Thus the concentration [H⁺] is greater than its value in pure water (10⁻⁷), and the pH of an acid solution is consequently less than 7. Similarly, in solutions of alkalis (which release OH⁻ ions) the pH is greater than 7. The pH of a solution is therefore a quantitative measure of its degree of acidity or alkalinity.

Solutions containing a weak acid (such equally acetic acrid H Ac) and a salt of it which is a strong electrolyte (eastward.g. sodium acetate, NaAc) have interesting backdrop. The completely dissociated salt yields a big quantity of Ac⁻ ions in the solution. From the equation of dissociation of the acid,

$\left[{\text{H}}^{+}\right]\left[{\text{Ac}}^{-}\right]/\left[\text{HAc}\right]=\mathrm{Yard},$

we find that the presence of backlog Air-conditioning⁻ ions in the solution causes a decrease in the number of H⁺ ions, i.eastward. inhibits the dissociation of the acid. The concentration [HAc] of undissociated acid molecules is therefore practically equal to the total concentration of the acid (denoted by c_a ). The concentration of Ac⁻ ions, which are nearly entirely supplied by the table salt, is practically equal to the salt concentration (c_s ). Thus [H⁺] = Kc_a /c _S, and the pH of the solution is

$\text{pH}=-{\log }_{10}\left[{\text{H}}^{+}\right]=-{\log }_{\mathrm{x}}K+{\log }_{10}\left(c_{\mathrm{due\; south}}/c_a\right).$

This depends but on the ratio of concentrations of the salt and the acrid. Thus dilution of the solution, or the improver of small quantities of any other acids or alkalis, has practically no effect on the pH of the solution. A solution of this type whose pH remains abiding is chosen a buffer solution.

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Physicochemical Devices and Reactors

Denis Constales , ... Guy B. Marin , in Advanced Data Assay & Modelling in Chemical Applied science, 2017

5.2.five Teorell's Approach

The mobility-based concept used by Einstein was further applied by Teorell (Teorell, 1935, 1937 ), who synthetic a theory on the diffusion of ions through membranes in aqueous solutions of univalent strong electrolytes (too meet Gorban et al., 2011). Teorell assumed the solutions to be ideal and homogeneous on both sides of the membrane. The essence of his approach is captured in the following equation:

(five.13) $\mathrm{Flux}=\left(\mathrm{mobility}\right)\times \left(\mathrm{concentration}\right)\times \left(\mathrm{forcefulness}\mathrm{per}\mathrm{kilo}\mathrm{gram}\mathrm{ion}\right)$

The force consists of ii parts: (i) a diffusion force acquired past a concentration gradient and (ii) an electrostatic forcefulness, caused past an electric potential gradient. With these 2 parts, Teorell'due south equation for the flux can be written as

(5.14) $J=\mathrm{one\; thousand}c\left(-R_{\mathrm{g}}T\frac{\mathrm{ane}}{c}\frac{\mathit{dc}}{dx}+q\frac{d\phi }{d\mathrm{10}}\right)$

where q is the charge and φ is the electrical potential.

It sometimes is convenient to stand for the improvidence part of the force in a unlike way, with c _eq as reference equilibrium concentration (Gorban et al., 2011):

(5.15) $-R_{\mathrm{thousand}}T\frac{1}{c}\frac{\mathit{dc}}{d\mathrm{10}}=-R_{\mathrm{k}}T\frac{dln\left(\frac{c}{c_{\mathrm{eq}}}\right)}{dx}$

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Volume 2

Robert K. Franklin , ... Richard B. Brown , in Comprehensive Microsystems, 2008

ii.12.4.1 Principle of Operation

To perform a voltammetric analysis, an excitation voltage is typically applied between two electrodes, and the current flowing through the cell is measured. Redox reactions must occur at both the electrodes in order to support the current flow; even so, only the reaction at the working electrode is of import. In most voltammetric analyses, the working electrode is a polarizable electrode, and the examination solution is a potent electrolyte and thus a good ionic usher. If the test solution is not a strong electrolyte, a groundwork electrolyte such as NaCl may be added to increment conductivity. Under these weather condition, the voltage applied to the solution primarily drops beyond the double layer. Since the double layer at the working electrode is extremely thin (≪  1   μm), big electric fields are adult in this area, providing the energy necessary to cause electron transfer and to drive the resulting redox reaction of the analyte material.

As discussed earlier, a generic redox reaction follows the form described by eqn [1] and the applied potential at which the rates for the forward and contrary reactions are equal and at which no internet electric current flows in the prison cell is determined past the Nernst equation (eqn [2]). If an external voltage is applied to the cell using the counter electrode, the forward and reverse rates for the redox reaction change, resulting in an increase of either O or R at the surface of the electrodes and a net electric current catamenia. Although eqn [2] applies simply to a system at equilibrium, when the cell is driven away from equilibrium, the basic human relationship described by eqn [two] nonetheless holds and the approximate ratio of O to R can be constitute by rearranging terms to go far at the following equation:

[5] $\frac{C_{\text{O}}}{C_{\text{R}}}=exp\left(\frac{\left(E^0-E\right)\text{<mi mathvariant="italic" is="true">nF</mi>}}{\text{<mi mathvariant="italic" is="true">RT</mi>}}\right)$

From this relation it is apparent that the input voltage required to push the reaction entirely to one side would be infinite. Nonetheless, since the relationship is logarithmic, the modify from having nearly all O to nearly all R at the surface is a very small alter in voltage. In fact, if the cloth exhibits a single electron reaction, an East that is only 177   mV greater than E ⁰ is large enough to make the ratio of a material thousand times greater than the other at the surface of the electrode (Kissinger et al. 1996).

The charge per unit at which the reaction proceeds and the magnitude of the faradaic current that flows are controlled by the following factors: the potential applied between the working electrode and the counter electrode; the electron transfer kinetics of the redox reaction; adsorption of ions on the surface of the electrode; and mass transfer of the reactant to the surface of the electrode and the product away from the electrode. Mass transfer occurs due to convection, diffusion, and migration. If the cell is mechanically isolated from vibration, mass transfer due to convection can be generally ignored, and if the background ionic strength of the solution is at least two orders of magnitude larger than that of the analyte, then most of the ionic current will be carried by background ions and mass transfer due to migration can besides be ignored. Assuming that mass transfer occurs mostly due to improvidence and that the improvidence of analyte to the electrode surface dominates the other rate-controlling steps, a closed-form solution of eqn [4] can normally exist plant that approximates the relationship betwixt the concentration of the analyte and the observed faradaic electric current.

The remainder of this department describes several of the voltammetric methods almost normally used with microfabricated sensors. All these methods adhere to the principles outlined in the preceding paragraphs, but differ in the excitation waveforms applied to the cell. The simplest method, chronoamperometry, which is presented start, consists of a single voltage step. After chronoamperometry is presented, an analysis of more complex methods such every bit linear sweep voltammetry (LSV), cyclic voltammetry, square wave voltammetry (SWV), and square wave anodic stripping voltammetry (ASV) are presented.

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twelfth International Symposium on Process Systems Engineering and 25th European Symposium on Computer Aided Process Applied science

Alexandre M. Teixeira , ... Ofélia Q.F. Araújo , in Computer Aided Chemical Engineering, 2015

3 MRU Implementation in Process Simulator

3.one Premises

Typical period rates and atmospheric condition reported in the literature of real MRUs were used for TP, FS and SS (Nazzer and Keogh, 2006). Operating force per unit area of Meg boiling systems was set at 0.2   bar abs (humid points ≤ 140°C) to avoid thermal degradation of MEG higher up 162°C. NaCl is the main ionic species, representing 1-3% w/west of Rich MEG, whereas other salts – CaCl_two, etc – reach only hundreds of ppm and are irrelevant in terms of thermal effects. Even so, NaCl was not included in the simulation for two reasons: (i) NaCl but settles in the wink-evaporator subsequently vaporization of 1000000 and H2o, which are responsible for the main energy effects associated with phase changes – to confirm this, MRU was imitation with/without NaCl and the differences in terms of heat duties were always found beneath ane-two% (Teixeira, 2014 ); (two) Aqueous solution models are non reliable with strong electrolytes at saturation, leading to inaccurate thermodynamic properties and ExA. Thus, after discarding NaCl, Rich MEG stream was defined as: 100t/d, 55%due west/w H _iiO   + 45%due west/due west One thousand thousand   at   25°C,   1   bar. The Slip Fraction in SS was chosen as l%. Temperature and pressure level of Rich and Lean Million have same values for TP, FS, SS. Thermodynamic calculations used the simulator Glycol Package.

three.ii Traditional Process (TP)

TP simply distillates water from Rich One thousand thousand via an atmospheric distillation column (ADC) with Lean MEG as bottoms. TP works well without formation water. However, with germination water in that location is aggregating of salts and dissolved minerals in the MEG loop overtime, leading to saturation and precipitations on exchangers, thermally degrading MEG. Effigy one depicts the simulation implementation of TP.

Figure i. TP Implementation

3.3 Full-Stream Process (FS)

FS treats Rich MEG with three serial steps: (i) Atmospheric Distillation Column (ADC) for a first removal of water below 140°C; (two) Wink-Evaporator (FLS) at 0.2 bar, wherein the feed instantaneously vaporizes after mixing with the recycled hot liquor, precipitating salt; and (iii) vapor from FLS goes to Sub-atmospheric Distillation Column (SDC) at   0.2   bar giving pure H₂O distillate and Lean MEG equally bottoms. Figure two illustrates the simulation implementation of FS.

Figure two. FS Implementation

3.4 Slip-Stream Procedure (SS)

SS combines TP with a smaller FLS-SDC train to treat the Slip Fraction of the effluent from TP section. An advantage of SS is the reuse of inhibitors and pH stabilizers, which are lost in the FS within the FLS solids. SS is suitable for low to intermediate water loads (Brustad et al., 2005). Effigy three shows the implementation of SS.

Figure 3. SS Implementation

3.5 Energy Consumption (EC)

EC was found for TP, FS and SS in Table 1, which also shows the respective Lean MEG composition. All heating duties stand for direct electricity consumptions as usual in offshore rigs (Myhre, 2001). TP has the lowest EC, as it is the simplest procedure with only one separation. On the other hand, FS has the highest EC. SS is the second as but function of the Rich MEG is evaporated.

Table 1. Electric Free energy Consumptions (EC) and Lean MEG Compositions for MRU Processes

Process	%w/due west MEG of Lean MEG	EC (kW)
TP	89.46	1685.73
FS	91.36	2330.38
SS	86.77	1894.l

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Boron Hydrides

Herbert Beall , Donald F. Gaines , in Encyclopedia of Physical Scientific discipline and Engineering science (Tertiary Edition), 2003

6.B Closo Anions

The properties of the closo ions, ${\text{B}}_6{\text{H}}_6^{2-}$ , ${\text{B}}_7{\text{H}}_7^{\mathrm{ii}-}$ , ${\text{B}}_{\mathrm{viii}}{\text{H}}_{\mathrm{viii}}^{2-}$ , ${\text{B}}_9{\text{H}}_9^{2-}$ , ${\text{B}}_{\mathrm{x}}{\text{H}}_{\mathrm{x}}^{\mathrm{ii}-}$ , ${\text{B}}_{\mathrm{11}}{\text{H}}_{\mathrm{11}}^{2-}$ , and ${\text{B}}_{12}{\text{H}}_{12}^{2-}$ , are roughly similar. We will concentrate on ${\text{B}}_{\mathrm{ten}}{\text{H}}_{10}^{2-}$ and ${\text{B}}_{\mathrm{12}}{\text{H}}_{\mathrm{12}}^{\mathrm{two}-}$ , the most familiar and best studied.

Small-scale unipositive cations such as Na⁺ and Chiliad⁺ form soluble salts with the ${\text{B}}_{10}{\text{H}}_{10}^{2-}$ and ${\text{B}}_{12}{\text{H}}_{12}^{\mathrm{ii}-}$ anions that are potent electrolytes. The anions are by and large isolated from solution as hydrates. Most dipositive cations such as Sr ²⁺ and Fe²⁺ practise the same. Big unipositive cations such Tl⁺ and (CH₃)_four  Due north⁺ form salts that are merely slightly soluble in water.

A large number of reactions in which H atoms are replaced by other substitutents are known, and the stability of the ${\text{B}}_{10}{\text{H}}_{\mathrm{x}}^{\mathrm{ii}-}$ and ${\text{B}}_{12}{\text{H}}_{12}^{2-}$ cages allows reactions under quite rigorous conditions to proceed with little or no muzzle degradation. Substitution reactions can be performed with ${\text{B}}_{10}{\text{H}}_{10}^{\mathrm{two}-}$ and ${\text{B}}_{12}{\text{H}}_{12}^{2-}$ salts or with H₃O⁺ counterions, i.e., the acid grade of the anion. Such acid catalysis often leads to facile reactions.

The acid forms of each of these closo anions tin can be fully deuterated in D₂O. Multiple replacement of hydrogen atoms past Cl, Br, and I occurs past reaction of the elemental halogen in the dark and tin can be forced to total replacement of all hydrogens. Elemental fluorine leads to extensive cage degradation. Substitutions in which nitrogen, oxygen, or sulfur atoms are fastened to the boron cage are known equally are reactions in which i substitutent is replaced past another. Examples are

$\begin{array}{lll}{[{\text{H}}_3\text{O}]}_2{\text{B}}_{12}{\text{H}}_{12}+\text{CO}\hfill & \to \hfill & {\text{B}}_{12}{\text{H}}_{11}{\text{CO}}^{-}\hfill \\ \hfill & \hfill & +\text{dicarbonylatedspecies}\hfill \\ {[{\text{H}}_{\mathrm{three}}\text{O}]}_2{\text{B}}_{12}{\text{H}}_{12}+{\text{CH}}_3\text{CN}\hfill & \to \hfill & {\text{B}}_{12}{\text{H}}_{11}{\text{NCCH}}_{\mathrm{iii}}\hfill \\ {[{\text{H}}_{\mathrm{three}}\text{O}]}_2{\text{B}}_{12}{\text{H}}_{12}+{\text{H}}_2\text{S}\hfill & \to \hfill & {\text{B}}_{12}{\text{H}}_{\mathrm{xi}}{\text{SH}}^{2-}\hfill \\ \hfill & \hfill & (\text{run across Section IX})\hfill \end{array}$

Note that although the ${\text{B}}_{12}{\text{H}}_{12}^{2-}$ has all equivalent boron atoms, the ${\text{B}}_{10}{\text{H}}_{10}^{\mathrm{two}-}$ ion does non. The ii boron atoms in upmost positions that cap the square antiprism are each side by side to only iv other boron atoms whereas the other 8 boron atoms in equatorial positions are each adjacent to 5 other boron atoms. In general, the equatorial boron atoms in ${\text{B}}_{10}{\text{H}}_{10}^{\mathrm{two}-}$ have substitutional reactivity similar to all of the boron atoms in ${\text{B}}_{12}{\text{H}}_{12}^{2-}$ , but the apical boron atoms in ${\text{B}}_{10}{\text{H}}_{\mathrm{ten}}^{2-}$ are more susceptible to some substitutions than the equatorial and less susceptible to others.

$\begin{array}{lll}{[{\text{H}}_{\mathrm{iii}}\text{O}]}_2{\text{B}}_{10}{\text{H}}_{10}+{\text{CH}}_3\text{CN}\hfill & \to \hfill & {\text{B}}_{10}{\text{H}}_9{\text{NCCH}}_3(\text{apical})\hfill \\ {[{\text{H}}_3\text{O}]}_2{\text{B}}_{10}{\text{H}}_{10}+{\text{NH}}_2\text{C}(\text{O})\text{H}\hfill & \to \hfill & {\text{B}}_{10}{\text{H}}_9\text{OC}({\text{NH}}_2)\text{H}\hfill \\ \hfill & \hfill & (\text{equatorial})\hfill \end{array}$

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Is O2 A Strong Electrolyte,

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