- Definition of NO2:
NO2, also known as nitrogen dioxide, is a very important and common chemical substance. The molecule of NO2 consists of one nitrogen atom (N) and two oxygen atoms (O). Therefore, the atomic mass of NO2 is 46.0055 u, in which the nitrogen atom has a mass of 14.0067 u and each oxygen atom has a mass of 15.9994 u. NO2 is structured as a nitrogen atom bonded to two oxygen atoms through covalent bonds. NO2 does not form ions in a non-molecular state, but it can form NO2- ions when reacting with other substances.
- Properties of NO2:
NO2 is a gas at room temperature and atmospheric pressure. NO2 is reddish-brown in color and has a pungent smell. NO2 is mildly acidic, so the pH of a NO2 solution in water typically ranges from 3 to 6. NO2 also has many special chemical properties, including the ability to react with metals, acids, non-metals, and salts.
- Common chemical reactions with NO2:
NO2 can react with metals, acids, non-metals, and salts. For example, NO2 can react with sodium metal (Na) to form sodium nitrite (NaNO2) and oxygen (O2) according to the reaction: 2Na + 2NO2 -> 2NaNO2 + O2. NO2 can also react with sulfuric acid (H2SO4) to form nitric acid (HNO3) and sulfur dioxide (SO2): 2NO2 + H2SO4 -> HNO3 + SO2.
- Synthesis of NO2:
NO2 can be synthesized in the laboratory or on an industrial scale. In the laboratory, NO2 is usually synthesized by reacting nitric acid (HNO3) with copper (Cu) according to the reaction: 4HNO3 + Cu -> Cu(NO3)2 + 2NO2 + 2H2O. On an industrial scale, NO2 is usually produced from oxygen (O2) and nitrogen (N2) in the air according to the reaction: O2 + 2N2 -> 2NO2.