Explain why h2 and o2

In cases where the reaction is more controlled, however, such as the consumption of hydrogen and oxygen in a fuel cell, the mechanism and kinetics of the O 2 reduction process can complicate issues greatly. For instance, the delivery of the protons and electrons derived from the ionization of hydrogen see redox half-reaction above to a molecule of oxygen has to be precisely controlled via a process know as proton-coupled electron transfer in order to ensure that the complete four-electron reduction of O 2 dominates.

Platinum metal is capable of serving as a catalyst that brandishes exquisite selectivity for the four-electron reduction of oxygen to water, and accordingly lies at the heart of fuel cell design and function. Given that platinum is rare and extremely expensive, current research is aimed at the development of structural and functional models for oxygen activation and reduction to water via proton-coupled electron transfer. Similar strategies are also being exploited to drive the energetically uphill reverse reaction, in which hydrogen is produced from water using solar energy.

The success of both these areas of work may ultimately prove crucial to the development and sustainability of a global hydrogen economy. Already a subscriber? Sign in. Thanks for reading Scientific American.

Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. On a submolecular level, the reason for the difference in energy levels between the reactants and products, lies with electronic configurations. Hydrogen atoms have one electron each. They combine into molecules of two so that they can share two electrons one each. This is because the inner-most electron shell is at a lower energy state and therefore more stable when occupied by two electrons.

Oxygen atoms have eight electrons each. They combine together in molecules of two by sharing four electrons so that their outer-most electron shells are fully occupied by eight electrons each. However, a far more stable alignment of electrons arises when two hydrogen atoms share an electron with one oxygen atom.

Only a small amount of energy is needed to "bump" the electrons of the reactants "out" of their orbits so that they can realign in the more energetically stable alignment, forming a new molecule, H2O. Following the electronic realignment between hydrogen and oxygen to create a new molecule, the product of the reaction is water and heat.

The heat can be harnessed to do work, such as driving turbines by heating water. The products are produced quickly due to the exothermic, chain-reaction nature of this chemical reaction. Like all chemical reactions, the reaction is not easily reversible. Clare Jackson is a freelance writer who started writing in and began writing for eHow in She writes on areas related to physics and health. With a background in scientific writing she tends to include lots of information in her articles.

Clare has a Master of Science in clinical research and a Bachelor of Science in physics. Simple Chemical Reactions in Fireworks. Hydrogen Fuel vs. Fossil Fuel. What Happens in the Light Reaction of Photosynthesis?

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