If hydrogen is nearly insoluble in water, why is water H2O then?
Hydrogen isn’t in solution when it is part of water. H2O means that in one water molecule, there are two hydrogen atoms and one oxygen atom, and the hydrogen atoms are both covalently bonded to the oxygen atom in the structure H-O-H. Water is therefore a compound. Solutions, such that are made when a solute is dissolved in a solvent, are mixtures and not compounds.