[Moneyking]

Hello I would like to know why Silicic acid is H4(SiO4) and not H2(SiO3).
thanks

[Araconan]

To my knowledge, Silicic acid actually refers to a group of acids formed from compounds that are composed of silicon oxides bonded to hydroxyl groups. The acids that you've stated, H₄SiO₄ and H₂SiO₃ are both known as 'silicic acid" (the name of the group) though their actual names are orthosilicic acid and metasilicic acid respectively.

H₄SiO₄ however is much more common, so maybe that's why your source is equivalating silicic scid to orthosilicic acid.