Tellurous acid is an inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 H₂TeO₃. It is the oxoacid

Oxoacid

An oxoacid is an acid that contains oxygen. To be more specific, it is an acid that:#contains oxygen#contains at least one other element#has at least one hydrogen atom bound to oxygen#forms an ion by the loss of one or more protons....

 of tellurium(IV). The compound is not well characterized. An alternative way of writing its formula is (HO)₂TeO. In principle, tellurous acid would form by treatment of tellurium dioxide

Tellurium dioxide

Tellurium dioxide is a solid oxide of tellurium. It is encountered in two different forms, the yellow orthorhombic mineral tellurite, β-TeO2, and the synthetic, colourless tetragonal , α-TeO2...

with water, i.e. hydrolysis. The related conjugate base is well known in the form of several salts such as potassium acid tellurite, KHTeO₃.