Free energy, definition pressure coefficient

In the definitions of T, two variables in addition to the ion chemical potential must also be specified as constant. In an equilibrium dialysis experiment, these are temperature and the chemical potential of water. This partial derivative is known as the Donnan coefficient. (Note that the hydrostatic pressure is higher in the RNA-containing solution.) In making connections between T and the Gibbs free energy, it is more convenient if temperature... 

Interpreting the Henry s Law coefficient can be confusing because of the number of different units used in the literature. In this text it is presented in units of moles per Idlogram so that the effect of pressure on volume in the ocean is normalized. Other units that are often used are molar (mol 1 ) and volume fraction at standard temperature (0°C) and pressure (latm) (ml 1 , STP). Be carefiil STP for gases and standard conditions for free energies are not the same The pressure terms are identical, but the temperatures are 0 and 25 °C, respectively. This is one of the casualties of an old science that evolved from many different laboratories. Since the volume of a mole of ideal gas at STP is exactly 22.4141, there is a direct relation between moles of gas and milliliters (STP) of gas. Another potential confusion is that the Henry s Law relation is sometimes referred to as the reciprocal of the value given here, e.g. 1 /Kh. We can only say that the bulk of marine literature follows the definition used in Eq. (3.51), and one should make careful note of the units when using this constant. 

In some of the American text-books definitions of the activity and activity coefficient are tised which are not quite identical with those adopted in the present chapter. The difference depends on the effect of total pressure on the free energy of a liquid phase and is usuaUy trivial unless the solution under discussion is at a pressure greatly in excess of one atmosphere. 

The integration constant g , the so-called chemical standard potential, is the partial molar free energy at a pressure P = 1 bar, temperature T and at an activity of unity. In an ideal mixture the activity coefficient is unity, so that the aforementioned definition holds for both real and ideal mixtures. 

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