THE EFFECT OF HYDRATION ON THE BASIC-ACID PROPERTIES OF OXIDES OF ELEMENTS

Abstract

Various definitions (by Brǿnsted – Lauri , Lux – Flood, Lewis )of the basicity – acidity for the systems of different types have been regarded. The necessity and possibility of the establishment of a general approach to definition of the mentioned parameter for binary demonstrated. A general character of the effect of hydration of basic and acidic oxides on the interrelation of their basic-acidic properties by Lux – Flood is established. As a parameter which reflects the expression of acidic properties, a value of the effective electronegativity of oxides and hydroxides of elements is proposed. The electronegativity of 3.0 for SO3 is chosen as principal one and values of other oxides were calculated from thermochemical data for sulfates of appropriate elements in analogous to L. Pauling manner for elements. Its values are 2.2-3.1 for acidic oxides, 0.3-1.6 for basic oxides and 1.7-2.1 for amphoteric oxides. Water is known as amphoteric oxide able to react both with acid and with basic oxides. The prevalence of acidic properties over basic ones for water is shown. It is caused by difference in energetic balance of the processes of accession to and removal from the H2O molecule of O2− ions. During the processes of hydration in the series oxide – hydroxide – hydroxide hydrate – aqueous solution a decrease of electronegativity in a case of acidic oxides and its increase in a case of basic oxides are observed. It has been shown equalizing (for basic-acidic differences) role of water concerning oxides of elements. A correlation between electronegativity of oxides and hydroxides of elements and basicity and acidity of their aqueous solution is established.

Keywords

• основно-кислотні властивості
• ефективна електронегативність
• оксиди та гідроксиди
• гідратація