How does Avogadro's law explain Gay-Lussac's law of combining volumes?
According to Avogadro's law under the same conditions of temperature and pressure, equal volumes of different gases have the same number of molecules.
since substances react in a simple ratio by a number of molecules, volumes of the gaseous reactants and products will also bear a simple ratio to one another.
Example:-
According to Gay-Lussac's Law
According to Avogadro's law