Electrolyte solution refers to the solution in which electrolyte dissolves into solvent and partially or completely dissociates into corresponding ions with positive and negative charges, and ions can move independently in the solution.Broadly speaking, solid ionic crystal materials also belong to the category of solutions, but unless otherwise specified, electrolyte solutions are only limited to liquid.[2]
Electrolyte solution refers tosoluteDissolved insolventAfter complete or partial dissociation into ionic solution.The solute iselectrolyte。Conductivity is the characteristic of electrolyte solution. Acid, alkali and salt solutions are all electrolyte solutions.The electrolyte solution is realized by the positively charged cations and negatively charged anions dissociated from the electrolyte, which move directionally towards the corresponding electrode under the action of an external electric field and discharge on it.Electrolyte conduction belongs to ionic conduction, and its size increases with temperature.Ionic conduction must cause electrolytic action at the electrode interface, causing changes in substances (related electrolytes).The metal conductors that usually rely on free electrons to conduct electricity are the first type conductors, while the electrolyte solutions and melts are called the second type conductors.
Factors affecting conductivity
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The main factors affecting conductivity include ionization degree, conductivity, ionic mobilityIon migration number, ionic activity and ionic strength.
Ionization degree
When the ionization equilibrium is reached, the ratio of the number of ionized electrolyte molecules to the total number of molecules is expressed as a percentage.A high degree of ionization indicates that there are many ions generated by dissociation and the conductivity is strong.At a certain temperature, the ionization degree of electrolyte increases with the decrease of its concentration.The quantitative relationship between ionization degree, concentration and ionization constant is determined by Ostwald's dilution law.Experiments show thatWeak electrolyteThe strong electrolyte basically does not obey the dilution law, because the strong electrolyte is practically completely ionized.There is no power balance problem in the solution.Because there is strong ion interaction in strong electrolyte solution (unless infinitely diluted solution), the ionization degree of strong electrolyte does not reflect the real situation of its ionization.Therefore, the ionization degree of strong electrolyte is called apparent ionization degree.
conductance
The reciprocal of resistance is consistent with the general meaning of conductance in electrotechnics.The conductance of electrolyte solution can be expressed in two ways: specific conductance and equivalent conductance.Specific conductance refers to the conductance of electrolyte with an electrode area of 1 square centimeter and an electrode distance of 1 centimeter.When two points reach, it refers to the conductivity of a solution containing 1g equivalent electrolyte between two parallel electrodes 1cm apart.
Ionic mobility
The moving speed of ions when the potential gradient between the two electrodes is 1V/cm, also called the absolute moving speed of ions.The ionic mobility decreases with the increase of solution concentration and increases with the increase of temperature.The greater the ionic mobility of the electrolyte, the greater its equivalent conductivity.
Ion migration number
The fraction of electricity transported by a certain ion migration in the total electricity passing through the solution is also called ion transmission fraction.The migration numbers of two ions with very different mobility are also very different.In industrial electrolysis, according to the mobility, the amount of conductive electricity of this kind of ion and the concentration change near the electrode can be judged as the basis for controlling electrolysis conditions.
Ionic activity
The corrected ion concentration, also called effective concentration, is equal to the product of the actual ion concentration and activity coefficient.The activity coefficient is equal to the ratio of activity to concentration.In addition to treating extremely dilute solutions, the concentration of ions is not equal to the activity, that is, the activity coefficient is not equal to 1, due to the complex interaction between ions in the solution and flux molecules.By introducing the concept of ion activity, that is, substituting ion activity for ion concentration, some thermodynamic formulas only applicable to ideal solutions can also be used in practical solutions.
ionic strength
The concentration of all ions in the solution multiplied by half of the sum of their valence squares.The average activity coefficient of ions decreases with the increase of ionic strength, and the higher the valence number of ions, the more it decreases.The ionic strength reflects the strength of the interaction between ions to a certain extent.[1]
