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2H 2 O → O 2 + 4H + + 4e − Oxidation (generation of dioxygen) 4H + + 4e − → 2H 2 Reduction (generation of dihydrogen) 2H 2 O → 2H 2 + O 2 Total Reaction Of the two half reactions, the oxidation step is the most demanding because it requires the coupling of 4 electron and proton transfers and the formation of an oxygen-oxygen bond.
At chemical equilibrium, the reaction quotient Q r of the product activity (a Red) by the reagent activity (a Ox) is equal to the equilibrium constant (K) of the half-reaction and in the absence of driving force (ΔG = 0) the potential (E red) also becomes nul. The numerically simplified form of the Nernst equation is expressed as:
The 4e − pathway reaction is the cathode reaction in fuel cell especially in proton-exchange membrane fuel cells, alkaline fuel cell and solid oxide fuel cell. While the 2e − pathway reaction is often the side reaction of 4e- pathway or can be used in synthesis of H 2 O 2 .
Thus, a reduction half reaction can be written for the O2 as it gains 4 electrons: O 2 ( g ) + 4 e − 2 O 2 − {\displaystyle {\ce {O2_{(g)}{}+ 4e- -> 2O^2-}}} The overall reaction is the sum of both half reactions:
A schematic representation of Clark's 1962 invention, the Oxygen Electrode. The Clark electrode [1] [2] is an electrode that measures ambient oxygen partial pressure in a liquid using a catalytic platinum surface according to the net reaction: [3] O 2 + 4 e − + 4 H + → 2 H 2 O
2h 2 o 4e − + 4h + + o 2 The protons are released into the thylakoid lumen , thus contributing to the generation of a proton gradient across the thylakoid membrane. This proton gradient is the driving force for adenosine triphosphate (ATP) synthesis via photophosphorylation and the coupling of the absorption of light energy and the oxidation ...
A concentration of just 23.5% oxygen, or roughly 2.5% above normal oxygen levels, can create an immediately hazardous condition due to the flammable nature of oxygen enriched environments.
Standard enthalpy of combustion is the enthalpy change when one mole of an organic compound reacts with molecular oxygen (O 2) to form carbon dioxide and liquid water. For example, the standard enthalpy of combustion of ethane gas refers to the reaction C 2 H 6 (g) + (7/2) O 2 (g) → 2 CO 2 (g) + 3 H 2 O (l).