Oxide equilibrium oxygen partial pressure over

Table 9.3 Equilibrium oxygen partial pressures over metal-oxide and binary oxide mixtures used as reference electrodes for thermodynamic measurements and sensors, and the standard free energy changes of the corresponding redox reactions [95, 96]...

The oxidation reaction will be influenced by the equilibrium oxygen pressure in the surroundings (Sections SI.5 and S3.2). Calculation of the equilibrium partial pressures over metal oxides shows that values lie between approximately 10 atmospheres to 10 " atmospheres. As the oxygen partial pressure in air is about a fifth of an atmosphere it is clear that metals will have a tendency to oxidise. From the point of view of thermodynamics, there is always a considerable driving force for reaction. 

Traces of water or oxygen in the inert atmosphere over the melts result in a reduction of the equilibrium concentration of oxide ions in ionic liquids, and favour the formation of other weaker bases such as (OW) or Oi. However, this mainly concerns the investigations with the use of the gas oxygen electrode, where the partial pressure of O2 over the melts is 1 atm. Even the use of simple drying routines for the preliminary treatment of the commercial inert gases allows one to avoid this error. 

In solution, a dissolved trace gas in equilibrium with the atmosphere would have the same partial pressure as the gas in the air. Its absolute concentration in terms of molecules or mass per unit volume of water depends on its solubility. Gas solubility varies over many orders of magnitude depending on the affinity of water for the gas molecules and the volatility of the gas. Gases range widely in their solubility in sea water, from the permanent gases like nitrogen (N2), oxygen (O2), nitrous oxide (N2O) and methane (CH4) that have a low solubility in sea... 

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