Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Law of independent ion

Conductivity measurements only define the sum of the equivalent ionic conductances no information about their individual values can be derived. However, it is known that the equivalent conductances of ions may differ significantly. According to Kohlrausch s law of independent ion drift, all ions move independent of each other in an infinitely diluted solution. Since the equivalent conductances of ions differ, they contribute differently to the current transport. The contribution of an ionic species i to the total current is called the transport number... [Pg.294]

At very low electrolyte concentrations, each ion of the electrolyte contributes independently to the molar conductivity. For an electrolyte of the form (A2+) (X2- ) , Kohlrausch s law of independent ion migration can be written as ... [Pg.43]

The following method for computing Ae will make this conception clear. As an example the value of A for acetic acid as a function of the ion concentration will be obtained. The computation depends upon two assumptions the evidence for which has been considered in this chapter. The assumptions are (a) aqueous solutions of sodium chloride, sodium acetate and hydrochloric acid are completely dissociated, and (6) at low ion concentrations the equivalent conductance, X, of the ion constituents of strong electrolytes are independent of the nature of the associated ions, i.ethey follow Kohlrausch s law of independent ion migration. Thus if completely dissociated acetic acid were capable of existence the value of its equivalent conductance Afl hac would be in accord with the relation 20 21-22... [Pg.344]

It is of interest to see whether Kohlrausch s law of independent ion migration which has been shown (page 340) to hold accurately for aqueous solutions is also valid for methyl alcohol solutions. Since transference data are not available a test similar to that for water solutions is not yet possible. If, however, limiting equivalent conductances are independent of the ions with which they are associated the differences of, for instance, the limiting conductances of the sodium and lithium salts of an acid HX should be independent of the nature of the radical X, since... [Pg.359]

In calculating conductivities, Kohlrausch s law of independent ion mobilities is assumed to be applicable, so conductivities may be calculated by summing up the equivalent conductivities of the separate anions and cations in the system. [Pg.741]

At the infinite dilution limit (c—>0) the dissociation is complete and the ion mobility only depends on the ion-solvent interactions and file ionic and the molar conductivities reach their infinite dilution values X° and A°, respectively. In fliis limit the Kohlrausch s law of independent ion migration (Kohlrausch, 1898)... [Pg.215]

In calculating conductivihes, Kohlrausch s law of independent ion mobilities is assumed to be applicable, so conduchvihes may be calculated by summing up the equivalent conductances of the separate anions and cahons in the system. In the non-suppressed mode, the solutes are revealed by the decrements in conductivity that they cause when the hydronium ions are replaced by the less conductive sodium and potassium ions ... [Pg.472]

This is known as the Law of independent ion migration, implying that, as drawn in Fig. 3.1, the cations and anions, move essentially independently of each other, to a good approximation. [Pg.57]

Each ion has its own characteristic mobiUty. The total conductivity of the electrolyte is the sum of the conductivities of the positive and negative ions. This is known as Kohlrausch s Law of Independent Migration of Ions. [Pg.509]

For strong electrolytes the molar conductivity increases as the dilution is increased, but it appears to approach a limiting value known as the molar conductivity at infinite dilution. The quantity A00 can be determined by graphical extrapolation for dilute solutions of strong electrolytes. For weak electrolytes the extrapolation method cannot be used for the determination of Ax but it may be calculated from the molar conductivities at infinite dilution of the respective ions, use being made of the Law of Independent Migration of Ions . At infinite dilution the ions are independent of each other, and each contributes its part of the total conductivity, thus ... [Pg.520]

The possibility of active transport of substances across membranes had first been pointed out in the middle of the nineteenth century by the physiologist Emil Heinrich du Bois-Reymond, a German of Swiss descent. The ability to accomplish active transport of ions and uncharged molecules in the direction of increasing electrochemical potentials is one of the most important features of cell membrane function. The law of independent ionic migration as a rule is violated in active transport. [Pg.578]

It may be added that Kohlrausch s law does not lead to any method of deducing the contributions of the individual ions. The immediate practical application of Kohlrausch s law of independent contributions of the ions at infinite dilution is a method for deducing the limiting equivalent conductance, A0, of weak electrolytes. This will be illustrated by taking a specific example of a weak electrolyte. [Pg.616]

This equation is valid for both strong and weak electrolytes, as a = 1 at the limiting dilution. The quantities A = zf- FU have the significance of ionic conductivities at infinite dilution. The Kohlrausch law of independent ionic conductivities holds for a solution containing an arbitrary number of ion species. At limiting dilution, all the ions conduct electric current independently the total conductivity of the solution is the sum of the contributions of the individual ions. [Pg.103]

We can recognize four main periods in the history of the study of aqueous solutions. Each period starts with one or more basic discoveries or advances in theoretical understanding. The first period, from about 1800 to 1890, was triggered by the discovery of the electrolysis of water followed by the investigation of other electrolysis reactions and electrochemical cells. Developments during this period are associated with names such as Davy, Faraday, Gay-Lussac, Hittorf, Ostwald, and Kohlrausch. The distinction between electrolytes and nonelectrolytes was made, the laws of electrolysis were quantitatively formulated, the electrical conductivity of electrolyte solutions was studied, and the concept of independent ions in solutions was proposed. [Pg.467]

When the limiting molar conductivities are to be obtained for a series of ions in a given solvent, the first step is to get the limiting molar conductivity of an ion by one of the above methods. Then, the limiting molar conductivities for other ions can be obtained sequentially by applying Kohlrausch s law of independent ionic migration (Section 5.8). [Pg.213]

Many substances dissolve in liquid sulfur dioxide to yield ionic, conducting solutions. It has been found that such conductance data extrapolated to very high dilution yield the limiting conductance of sulfur dioxide. Both the Ostwald dilution law and the law of independent mobility of ions hold for strong" electrolytes in highly dilute solutions. [Pg.500]

On the other hand the equivalent conductance of weak electrolytes rises much steeper on dilution yet it doesn t nearly attain its limit value A° at concentrations mentioned in the previous case. As the measurement of the conductance at still higher dilution is extremely inaccurate due to high resistances of the solution, the same method of extrapolation as used with the strong electrolytes is unsuitable for determination of A0 of weak electrolytes. In such cases we resort to the Kohlrausch law of independent migration of ions, to l e discussed further on. [Pg.37]

Limiting laws in science are tho,se that hold under limiting conditions such as dilute solutions. In addition to Beer s law, other limiting laws in chemistry include the Debye-Huckel law (see Chapter 10) and the law of independent migration, which describes the conductance of electricity by ions. [Pg.729]

Table IV. Test op Kohlratjsch s Law op Independent Ion Migration for Salt Solutions in Methyl Alcohol at 25° Values of A2o "... Table IV. Test op Kohlratjsch s Law op Independent Ion Migration for Salt Solutions in Methyl Alcohol at 25° Values of A2o "...
Kohlrausch explained this behavior in terms of his law of independent jnigration of ions. Each ion is assumed to make its own contribution to the molar conductivity, irrespective of the nature of the other ion with which it is associated. In other words. [Pg.276]

The measurement of the conductivity yields the sum of the positive and negative ion conductivities. To obtain the individual ion conductivities, an additional independent measurement is necessary. Even bef ore Kohlrausch demonstrated the law of independent migration of ions, it was commonly supposed that each ion contributed to the flow of current. In 1853 Hittorf devised a method to measure the contribution of the individual ions. [Pg.775]

The A° values are not accessible to direct measurement, but they may be calculated from transport numbers. Kohlrausch s law of independent ionic conductivities states that at low electrolyte concentrations the conductivity is directly proportional to the sum of the n individual ion contributions, that is. [Pg.971]

Kohlrauch also established the law of independent mobilities of ions at infinite dilution. This implies that To at infinite dilution is a constant at a given temperature and will not be affected by the presence of other ions in the electrolytes. This provides a practical estimation of the value of from the values of XJ... [Pg.86]

Only in strongly diluted solutirms where there are no noticeable interactions between the ions do the individual ions move in the electric field independently of the type of counter-irMis. This law of independent migration of ions was found by the German physicist Friedrich Kohlrausch in the nineteenth century. [Pg.506]

Conversely, Eq. (21.42) can be used to determine the degree of dissociation a of a weak electrolyte at a given concentration c by measuring the molar conductivity. Moreover, with the help of Eq. (21.41), the equilibrium constant of the substance becomes accessible. However, for these calculations we need the limiting molar conductivity A . This quantity is very difficult to find experimentally because the steep rise of the A at low concentrations makes an extrapolation to infinite dilution very uncertain. The law of independent migration of ions [Eq. (21.35)] offers a way out. hi the case of infinite dilution, the limiting molar conductivity of acetic acid is the sum of the contributions of cation and anion ... [Pg.511]


See other pages where Law of independent ion is mentioned: [Pg.366]    [Pg.125]    [Pg.366]    [Pg.125]    [Pg.615]    [Pg.505]    [Pg.156]    [Pg.15]    [Pg.56]    [Pg.443]    [Pg.77]    [Pg.670]    [Pg.92]    [Pg.53]    [Pg.348]    [Pg.53]    [Pg.101]    [Pg.57]    [Pg.368]    [Pg.286]   


SEARCH



Kohlrausch’s law of independent ion

Kohlrausch’s law of independent ion migration

Law of independent ion migration

© 2024 chempedia.info