Strong electrolytes defined

Which electrolytes are called strong, and which are called weak In what form can the law of mass action be applied to strong electrolytes Define the activity, the activity coefficient, and the ionic strength of a solution. 

Arrhenius postulated in 1887 that an appreciable fraction of electrolyte in water dissociates to free ions, which are responsible for the electrical conductance of its aqueous solution. Later Kohlrausch plotted the equivalent conductivities of an electrolyte at a constant temperature against the square root of its concentration he found a slow linear increase of A with increasing dilution for so-called strong electrolytes (salts), but a tangential increase for weak electrolytes (weak acids and bases). Hence the equivalent conductivity of an electrolyte reaches a limiting value at infinite dilution, defined as... 

Electrolytes are defined as substances whose aqueous solutions conduct electricity due to the presence of ions in solution. Acids, soluble bases and soluble salts are electrolytes. Measuring the extent to which a substance s aqueous solution conducts electricity is how chemists determine whether it is a strong or weak electrolyte. If the solution conducts electricity well, the solute is a strong electrolyte, like the strong acid, HC1 if it conducts electricity poorly, the solute is a weak electrolyte, like the weak acid, HF. 

At the microscopic level, the Arrhenius theory defines acids as substances which, when dissolved in water, yield the hydronium ion (H30+) or H+(aq). Bases are defined as substances which, when dissolved in water, yield the hydroxide ion (OH). Acids and bases may be strong (as in strong electrolytes), dissociating completely in water, or weak (as in weak electrolytes), partially dissociating in water. (We will see the more useful Brpnsted-Lowry definitions of acids and bases in Chapter 15.) Strong acids include ... 

To make the basic Pitzer equation more useful for data correlation of aqueous strong electrolyte systems, Pitzer modified it by defining a new set of more directly observable parameters representing certain combinations of the second and third virial coefficients. The modified Pitzer equation is... 

From the point of view of chemical modeling, aqueous solutions are treated as electrolytic solutions —i.e., solutions in which solutes are present partially or totally in ionic form. Speciation is the name for the characteristic distribution of ion species in a given aqueous solution in the form of simple ions, ionic couplings, and neutral molecules. Solutes in aqueous solutions are defined as electrolytes and may be subdivided into nonassociated and associated. Nonassociated electrolytes are also defined as strong and mainly occur in the form of simple or simply hydrated ions. An example of a strong electrolyte is the salt NaCl, which, in aqueous solution of low ionic strength, occurs in the form of completely dissociated Na and CN ions. 

These equations are used whenever we need an expression for the chemical potential of a strong electrolyte in solution. We have based the development only on a binary system. The equations are exactly the same when several strong electrolytes are present as solutes. In such cases the chemical potential of a given solute is a function of the molalities of all solutes through the mean activity coefficients. In general the reference state is defined as the solution in which the molality of all solutes is infinitesimally small. In special cases a mixed solvent consisting of the pure solvent and one or more solutes at a fixed molality may be used. The reference state in such cases is the infinitely dilute solution of all solutes except those whose concentrations are kept constant. Again, when two or more substances, pure or mixed, may be considered as solvents, a choice of solvent must be made and clearly stated. 

The original form of the Debye-Hiickel equation permits the calculation of the mean activity coefficients of strong electrolytes in solutions defined by their molarity c. Should the value of this coefficient be expressed by molality, whioh is more advantageous in electrochemistry, it will be possible in the case of a sufficiently diluted solution to substitute into the equation (V-58) for = y m (see V-41e) and for molarities of all ions the product of their molalities and the density of the solvent s wqp°, so that ... 

When one first thinks of the electrical double layer (edl) one imagines the description conceived by the originators, Debye and Huckel [2], Gouy and Chapman [3], Verwey and Overbeek [1], of a sharp and well-defined boundary between two phases. One of the phases usually being an aqueous medium in which a strong electrolyte is dissolved to a molar concentration of cs. The other phase is usually a solid, impermeable to either the electrolyte... 

Having defined various activities and activity coefficients in solutions made up from strong electrolytes we now turn to the determination of 7. For this purpose we briefly discuss some aspects of the Debve—Huckel Theory. 

The procedure now consists in adding other strong electrolytes to the solution. Since remains unaffected by this step while of the electrolyte of interest necessarily changes, m will change in the opposite direction. One thus measures m from the observed solubilities of the salt My Ay in the presence of other salts added in varying amounts. The results may then be extrapolated to infinite dilution on a plot of m versus where S is the ionic strength defined in Eq. (4.2.1). This permits an extrapolation to zero molarity where y — 1. The mean molarity obtained from this extrapolation thus yields. Measuring m for any other value of S then provides the desired y ... 

For dissolved species the standard state is defined as an ideal solution with a concentration of 1 M (this is obtained in practice by extrapolating the dilute solution behavior up to this concentration). A special comment is in order on the standard enthalpies of formation of ions. When a strong electrolyte dissolves in water, both positive and negative ions form it is impossible to produce one without the other. It is therefore also impossible to measure the enthalpy change of formation of ions of only one charge. Only the sum of the enthalpies of formation of the positive and negative ions is accessible to calorimetric experiments. Therefore, chemists have agreed that AH° of H (aq) is set to zero. 

This relationship is frequently employed to define the activity 02 of a strong electrolyte in terms of the activities of the constituent ions. 

Step 2. Define the Unknown Calcium oxalate is a strong electrolyte, so that its molar analytical concentration is equal to the equilibrium calcium ion concentration. That is. 

Define and distinguish among (a) strong electrolytes, (b) weak electrolytes, and (c) nonelectrolytes. 

Define and illustrate the following terms clearly and concisely. Give an example of each, (a) strong electrolyte (b) weak electrolyte (c) nonelectrolyte (d) strong acid (e) strong base (f) weak acid (g) weak base (h) insoluble base. 

Suspensions of the colloidal-sized oxyhydroxides can be destabilized by increases in ionic strength (strong electrolyte concentrations) such as occur when a stream enters an estuary (Fig. 12.5). Small amounts of specifically adsorbed species at well-defined concentations can also destabilize the suspended oxyhydroxides. 

Define the mean ion activity coefficient of a salt and comment on its significance in a weak versus a strong electrolyte solution. 

For low-molecular strong electrolytes the concentration dependence of equivalent conductivity is simple and universal. From a well-defined limiting value the equivalent conductivity decreases monotonically with increasing concentration, although the conductivity curves normally exhibit a distinct curvature, as the decrease levels off at high concentrations. The decrease of equivalent conductivity in these solutions is a result of increased interionic friction, which increases as the interionic distances decrease with increasing concentration. 

How can we predict whether a precipitate will form when a compound is added to a solntion or when two solutions are mixed It depends on the solubility of the solute, which is defined as the maximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature. Chemists refer to substances as soluble, slightly soluble, or insoluble in a qualitative sense. A substance is said to be soluble if a fair amount of it visibly dissolves when added to water. If not, the substance is described as slightly soluble or insoluble. All ionic compounds are strong electrolytes, but they are not equally soluble. 

As defined in Section 4.3, a salt is an ionic compound formed by the reaction between an acid and a base. Salts are strong electrolytes that completely dissociate into ions in water. The term salt hydrolysis describes the reaction of an anion or a cation of a salt, or both, with water. Salt hydrolysis usually affects the pH of a solution. 

COMPARISON OF SALT EFFECTS. In order to illustrate the effect of dissolved salts on the solubility of both volatile strong electrolytes and neutral species, conditional Henry s law constants Kh, K h are defined for the two solute types such that ... 

Define and illustrate the following terms clearly and concisely. Give an example of each, (a) strong electrolyte ... 

The problem of defining activities is somewhat rnore complicated in electrolytic solutions than in solutions of nonelectrolytes. Solutions of strong electrolytes exhibit marked deviations from ideal behavior even at concentrations well below those at which a solution of a nonelectrolyte would behave in the ideal dilute way. The determination of activities and activity coefficients has a correspondingly greater importance for solutions of strong electrolytes. To simplify the notation as much as possible a subscript s will be used for the... 

The beginning of the modern approach to strong-electrolyte solutions was G. N. Lewis (1913) empirical observation that y depends approximately only on the total ionic strength, T, of the solution and not on the specific ions present. The total ionic strength is defined by the equation... 

Define the term strong electrolyte. What types of substances tend to be strong electrolytes What does a solution of a strong electrolyte contain Give a way to determine if a substance is a strong electrolyte. 

Meissner and Kusik (M2) presented, in 1972, a method of calculating the reduced activity coefficients of strong electrolytes in a multicomponent solution. They based their method on Br0nsted s proposal that, in multicomponent solutions, the activity coefficient of an electrolyte will be influenced most by the interaction of it s cation with all the anions in solution and the interaction of it s anion with all the cations in solution. Ignoring the possible interactions between like charged ions was felt to be valid as such interactions would be very small. Meissner and Kusik proposed that the activity coefficient could then be defined as ... 

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