Step 2: Analyze the oxidation states of the metal in each oxide. For CrO, chromium is in the +2 oxidation state, and in Cr2O3, it is in the +3 oxidation state. For SnO2, tin is in the +4 oxidation state, and in SnO, it is in the +2 oxidation state. For As2O3, arsenic is in the +3 oxidation state, and in As2O5, it is in the +5 oxidation state.