Ammonia free energy changes

Let us define the respective basicity by — AG in the gas phase and — AG" in aqueous solution. For discussions concerning the relative strength in basicity of a series of methyl-amines, only the relative magnitudes of these quantities are needed. Thus the free energy changes associated with the protonation of the methylamines relative to those of ammonia are defined as... 

The production of ammonia is of historical interest because it represents the first important application of thermodynamics to an industrial process. Considering the synthesis reaction of ammonia from its elements, the calculated reaction heat (AH) and free energy change (AG) at room temperature are approximately -46 and -16.5 KJ/mol, respectively. Although the calculated equilibrium constant = 3.6 X 108 at room temperature is substantially high, no reaction occurs under these conditions, and the rate is practically zero. The ammonia synthesis reaction could be represented as follows ... 

Because the free-energy change for any process at constant temperature and pressure is AG = AH — TAS, we can calculate the standard free-energy change AG° for a reaction from the standard enthalpy change AH0 and the standard entropy change AS°. Consider again the Haber synthesis of ammonia ... 

Calculate the free-energy change for ammonia synthesis at 25°C (298 K) given the following sets of partial pressures ... 

The gas-phase basicity GB of B is the negative of AGH+(g), the standard free-energy change for the reaction described in equation 42. All GBs are referred to ammonia. 

For chemical reactions we are often interested in the standard free energy change (AG°), the change in free energy that occurs if the reactants in their standard states are converted to the products in their standard states, For example, for the ammonia synthesis reaction at 25°C,... 

In environmental engineering, it is customary to call the substance oxidized as the electron donor and the substance reduced as the electron acceptor. The electron donor is normally considered as food. In the context of nitrogen removal, the foods are the nitrites, nitrates, and ammonia. Equation (15.10) is an example of an electron donor reaction. Zn is the donor of the electrons portrayed on the right-hand side of the half-cell reaction. On the other hand, the reverse of the equation is an example of an electron acceptor reaction. Zn would be the electron acceptor. McCarty (1975) derived values for free energy changes of half-reactions for various electron donors and acceptors utilized in a bacterial systems. The ones specific for the nitrogen species removal are shown in Table 15.2. 

Section 5.6) to calculate the enthalpy, entropy, and free-energy changes that occur for en to replace ammonia as ligands on Cu(ll) ... 

Ammonia can react with oxygen gas to form nitrogen dioxide and water, (a) Write a balanced chemical equation for this reaction, (b) Use tabulated data to determine the free energy change for the reaction and comment on its spontaneity, (c) Use tabulated data to calculate the enthalpy change of the reaction. 

Free energy changes relative to ammonia for ionization of methyl amines in the gas phase and in water ... 

The group of microorganisms known as autotrophic bacteria obtain energy from the oxidation of a variety of inorganic compounds (ammonia, nitrite, sulfide, ferrous iron, hydrogen, carbon monoxide, sulfur, thiosulfate).The free energy changes and over-all efficiencies of a number of these processes have been calculated. We may take as an example the oxidation of nitrite to nitrate performed by Nitrobacter... 

Figure 1. Gas-phase proton-transfer reactions base strengths relative to ammonia, for typical step sequences in standard free energy changes, at 298 K.

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