Silicic acid

Silicic acid /sɪˈlɪsɪk ˌæsɪd/ is the general name for a family of chemical compounds containing the element silicon attached to oxide and hydroxyl groups, with the general formula n. They are generally colorless and sparingly soluble in water. They are very weak acids, often polymeric, whose conjugate bases are the silicate ions.

Two important members of this class are orthosilicic acid H
and the polymeric metasilicic acid n. No pure silicic acids have been isolated, but they exist in dilute water solutions (including seawater), and play important roles in biology and technology.

Silicic acid was invoked by Jöns Jacob Berzelius in the early 19th century to explain the interaction between silicon dioxide (silica) and water, namely the hydration reaction

The silicon-oxygen double bond implied by the formula H
is hypothetical or highly unstable, and the "silicic acid" above usually polymerizes and/or is further hydrated. For example,


Like other silanols, silicic acids are weak acids. Since no inorganic silicic acid has been purified, the reactivity of these species is inferred rather than observed. In concentrated solutions, generally silicic acids polymerize and ultimately degrade to silicon dioxide and water.

This page was last edited on 17 May 2018, at 13:08.
Reference: under CC BY-SA license.

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