Chemical change, direction potential

We now consider briefly the matter of electrode potentials. The familiar Nemst equation was at one time treated in terms of the solution pressure of the metal in the electrode, but it is better to consider directly the net chemical change accompanying the flow of 1 faraday (7 ), and to equate the electrical work to the free energy change. Thus, for the cell... 

Introduction Chemical reactivity is the tendency of substances to undergo chemical change. A chemical reactivity hazard is a situation with the potential for an uncontrolled chemical reaction that can result directly or indirectly in serious harm to people, property, or the environment. A chemical reaction can get out of control whenever the reaction environment is not able to safely absorb the energy and products released by the reaction. The possibility of such situations should be anticipated not only in the reaction step of chemical processes but also in storage, mixing, physical processing, purification, waste treatment, environmental control systems, and any other areas where reactive materials are handled or reactive interactions are possible. 

On January 1, 1977, the chemical industry truly became a regulated industry. The environmental laws up until that time had covered some chemicals, but had been media oriented. That is — they were concerned about certain chemicals that escaped as emissions or pollutants to various media - the air, our water, contaminated our food or entered the workplace. TSCA changed that direction. It was designed to regulate commerce on chemical substances. TSCA potentially applies to all chemicals manufactured, processed, distributed or used in the U.S. except those chemicals already regulated under certain other federal laws. TSCA affects not only the chemical industry itself, but the many other industries whose products are chemical in nature. This includes most all industrial products. 

The use of AG as a criterion for deciding the direction of a chemical change has been briefly mentioned. AG"" refers to the reaction with both products and reactants in their standard states and industrial processes are, of course, often carried out under conditions far removed from standard. The significance of AG"" in relation to the technical feasibility of a reaction is illustrated in Table 1 where it is seen that AG = + 20 kJ mol" means an equilibrium constant of 3 x 10 at 298 K. With such a small equilibrium constant, a reaction is unlikely to be of much industrial value. At 2000 K, however, the same value of AG"" leads to an equilibrium constant of 0.3, potentially a very much more attractive situation. 

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