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How do molecular oxides form oxyacids when they react with water?

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Two diagrams show the three-dimensional structure of a methane molecule: panel A uses a ball-and-stick model with a central carbon atom connected to four hydrogen atoms in a tetrahedral arrangement, while panel B illustrates the bond angle of 109.5 degrees and bond length of 1.09 angstroms between carbon and hydrogen atoms. — chemical compound Methane, in which four hydrogen atoms are bound to a single carbon atom, is an example of a basic chemical compound. The structures of chemical compounds are influenced by complex factors, such as bond angles and bond length.

Molecular oxides, specifically nonmetal oxides, react with water to form oxyacids through two primary mechanisms.12

Acid Anhydrides

Many nonmetal oxides, such as sulfur trioxide ( $S O_{3}$ ) and dinitrogen pentoxide ( $N_{2} O_{5}$ ), are known as acid anhydrides. When these compounds react with water, they form the corresponding oxyacid without any change in the oxidation number of the nonmetal atom. For example:1
$N_{2} O_{5} + H_{2} O \to 2 H N O_{3}$

Disproportionation Reactions

In cases where the nonmetal does not exhibit one of its common oxidation numbers—such as nitrogen dioxide ( $N O_{2}$ ) or chlorine dioxide ( $C l O_{2}$ )—the reaction with water involves a disproportionation process. In this reaction, the nonmetal is simultaneously oxidized and reduced, meaning its oxidation number increases in one product and decreases in another. For example:1
$3 N O_{2} + H_{2} O \to 2 H N O_{3} + N O$

These resulting oxyacids are characterized by their ability to yield hydronium ions ( $H_{3} O^{+}$ ) when in an aqueous solution.12