Question

How to oxygen earth on oxygen mass is low in carbohydrates ?

Answer 1

Oxygen makes up one fifth of the atmosphere, with the remainder being mostly nitrogen. About 89% of the mass of the oceans is oxygen, and oxygen is the most abundant element in the Earth's crust accounting for almost half its total mass. In fact, most of the rocks on Earth are composed of oxygen-rich silicates, such as forsterite(Mg2SiO4), pyroxene (Fe2SiO4) and olivine (MgFeSiO4). Although nowadays, oxygen is abundant in the atmosphere, this was not always true. The atmosphere of the newly-formed earth contained mainly carbon dioxide and sulphur compounds. Oxygen only made an appearance when the first single-celled lifeforms evolved. These blue-green bacteria (prokaryotes) split water into hydrogen and oxygen (discarding the oxygen), and also liberate oxygen from CO2 in the process of making carbohydrates. Thus the oxygen in the atmosphere was originally a waste product - a pollutant - of the primeval planet. The vast quantities of O2 that were released by these photosynthetic processes oxidised the iron in the seas and, in effect, the Earth rusted! We can date this event by the great deposits of red iron ore that are found deep underground in certain regions of the world.

Answer 2

the recombination of oxygen atoms and isotopic exchange with molecular oxygen. The simplest heterogeneous catalytic process involving molecular oxygen is the dissociation of O2 into atoms together with the reverse reaction, the recombination of O-atoms. As the dissociation reaction is highly endothermic, temperatures greater than 1000° C are required before appreciable rates of reaction are observed and this restricts the range of catalysts that can be studied. At low pressures and at temperatures of 1000°-1500° C, the reaction proceeds on platinum via the dissociative oxygen chemisorption of oxygen and the desorption of O-atoms. The surface coverage with atomic oxygen is assumed to be low on account of the high temperature. The interaction of atoms or radicals is known to proceed rapidly even without a catalyst, but the large amount of heat evolved in reaction favors decomposition of the product. Solid catalysts, as third bodies, adsorb the energy released and dissipate it, stabilizing the O2 molecule formed. At the same time, a catalyst takes part in intermediate chemical reactions with the O-atoms and, as a result, the specificity of different surfaces is manifested.