Which of the following compounds is known as metasilicic acid?

Metasilicic acid (H₂SiO₃) is one of the hydrated forms of silicic acid, a weak acid derived from silicon dioxide (SiO₂). In inorganic chemistry, silicic acids represent a group of compounds formed when silica reacts with water under specific conditions. The general formula of metasilicic acid can be written as H₂SiO₃, which corresponds to the simplest polymeric form among silicic acids.

When silicon dioxide (SiO₂) is treated with hot water, a partial hydrolysis occurs:
SiO₂ + H₂O → H₂SiO₃

Metasilicic acid is weakly acidic, sparingly soluble in water, and exists mostly in colloidal or polymeric forms rather than as discrete molecules. It readily dehydrates upon heating to form silica again. This reversible reaction demonstrates the relationship between silica and silicic acids in nature and laboratory processes.

Chemically, metasilicic acid behaves as a weak acid that forms salts known as metasilicates (e.g., sodium metasilicate Na₂SiO₃ and calcium metasilicate CaSiO₃). These compounds are widely used in detergents, ceramics, cements, and glass industries due to their stability and ability to form silicate networks.

Other options in the question refer to acids of different elements:

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  H₂SnO₃ – Metastannic acid (acid of tin)

  
  


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  H₃AsO₄ – Arsenic acid

  
  


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  H₃SbO₄ – Antimonic acid

  
  

These are chemically unrelated to silicic acids.

Thus, H₂SiO₃ is specifically known as metasilicic acid, an important compound in the study of silicon chemistry and the structure of silicates, which are key components of the Earth’s crust. Its understanding helps explain the chemical foundation of natural silicate minerals and synthetic materials like glass and ceramics