Regrettably, there is no chemical substance with the formula H2O4. This may be a mistake in writing the formula.
However, there is a similar chemical substance, that is H2O2, also known as hydrogen peroxide or oxygenated water. Hydrogen peroxide is a colorless liquid with a distinctive smell and strong oxidizing ability. The molecular weight of this substance is 34.0147 g/mol.
It is synthesized through the electrolysis process of a sulfuric acid substrate containing an oxidizer. This is how hydrogen peroxide is prepared in the laboratory. On an industrial scale, it is usually produced from the oxidation process of reducing substances like anthraquinone.
In chemical reactions, hydrogen peroxide reacts with various metals, acids, nonmetals, and different salts. A typical example is its reaction with iodine to produce iodine and water.
However, if you want to learn about a specific chemical substance with the formula H2O4, I suggest you check the information again or search from another source.