Now here is a question for you. Atomic oxygen, O, is extremely short-lived because it dimerizes to give stable O2
molecules. Nonetheless, oxygen atoms have been detected experimentally. Do you think atomic oxygen can be identified as another allotropic form of oxygen? [My answer: Why not? The experimental demonstration of atomic oxygen shows that it can exist under certain conditions.] 1.10.3. Applications of Oxygen.
Pure oxygen is broadly used for the smelting of iron ores into steel, metal cutting and welding, for rocket fuels, for making chemicals, and in medicine. 1.10.4. Physical Properties of O2.
Oxygen is a colorless and odorless gas that is slightly more dense than air. At normal pressure (1 atmosphere), the boiling point of oxygen is -183 o
C. Liquid oxygen is light blue in color. At -219 o
C oxygen becomes a solid. 1.10.5. Preparation of Oxygen.
In industry, pure oxygen is isolated from air by low-temperature (cryogenic) distillation or in a different process that is called vacuum swing adsorption. In the laboratory, oxygen is often obtained by heating potassium permanganate, KMnO4
, according to the following equation.2 KMnO4 = K2MnO4 + MnO2 + O2↑
(watch this video
Small quantities of O2
can also be prepared by the decomposition of hydrogen peroxide in the presence of a catalyst, such as MnO2
or baker's yeast (see Section 1.8, including Experiment 5):2 H2O2 = 2 H2O + O2↑ 1.10.6. Chemical Properties of O2.
Without oxygen in the atmosphere, there would be no life. The oxygen that we breathe is needed for many vital bioprocesses continuously occurring in our body. These bioprocesses are multistep chemical transformations, which, due to their complexity, are studied in advanced biochemistry and chemistry courses. In our introductory course, we will consider only very simple reactions of O2
As demonstrated in this video
, flammable substances burn in pure oxygen more rapidly and brightly than in air, which contains only about 20% O2
. Among simple substances, hydrogen (H2
), carbon (C), sulfur (S), phosphorus (P), magnesium (Mg), aluminum (Al), and even iron (Fe) react with oxygen to produce the corresponding oxides
of these elements (Figure 1-33). Among the limited number of simple substances that do not react with O2
are some precious metals, such as gold and platinum.