H2Cr5O11 is not a real chemical substance and therefore does not have a specific name, properties, or method of preparation.
However, based on the chemical formula, we can assume that it might be a compound of hydrogen, chromium and oxygen. In its formula, there are 2 atoms of hydrogen, 5 atoms of chromium and 11 atoms of oxygen.
Nevertheless, this substance does not exist in reality as chromium can only form compounds with no more than 6 oxygen atoms.
Therefore, it’s hard to determine the specific physical and chemical properties of H2Cr5O11. We also can’t determine its specific molecular structure.
In case you’re looking for information about a specific different chemical substance, please provide its exact name or chemical formula so we can provide the most accurate information.