The increasing order of acidic oxides of Cr follows the trends

The oxidation states of Cr in the given oxides are in the order +6, +2 and + 3, respectively. Therefore,$\mathrm{CrO}<{\mathrm{Cr}}_2{\mathrm{O}}_3<{\mathrm{CrO}}_3$ This is because, the acidity of the oxides made from the same metal increases with increases in the oxidation number of the metal. the increasing order of acidity The acidic character of oxide increases with increasing oxidation state of the metal ion.