Question

Why is the reaction SO2 + H2O → H2SO2 not balanced?

Answer 1

There are more oxygen atoms in the reactants while there are less oxygen atoms in the product.

Both sides of the equation is supposed to be balanced for a balanced equation. If any one of them isn't balanced, the equation remains unbalanced.

The main reason why the reaction above can not be balanced is:

This chemical reaction SO2 + H2O -> H2SO2 is not correctly written.

It must be: SO2 + H2O -> H2SO3

hope this helps....