Select oxides and salts from the proposed list: SO3; H2SO4; Na2SO4; ZnSO4; NO2; HNO3; KNO3.

From the above list, we need to select separately salts, separately oxides. First, choose the salt. We can attribute the following substances from the list to salts: Na2SO4 – sodium sulfate, sodium metal salt and sulfuric acid. ZnSO4 – zinc sulfate, zinc metal salt and sulfuric acid. KNO3 – potassium nitrate, potassium metal salt and nitric acid.
Now select oxides from the list. Oxides include SO3 – hexavalent sulfur oxide, a compound of sulfur and oxygen, NO2 – tetravalent nitrogen oxide, a compound of nitrogen and oxygen.