Exothermic energies

Fig. 8A. The exothermic energy release of shocked but unreacted Ni-Al mixtures shows a profound change. A preinitiation" phenomenon in which reaction temper ture is reduced by over 200 °C is caused by the shock process. A compact composer of composite particles that inhibit mixing shows no such effect [88H01].

Exothermic energy transferred from system to surroundings... 

Because the temperature rises, the process is exothermic, energy leaves the system as heat and AU = —0.6 14 kj. 

A simplified method for near-quantitative estimation of the exothermicity (energy of exothermic decomposition /unit mass) of products or reaction mixtures, which is suitable for a hand-calculator, is presented. It is based on the difference between the total energies of atomization of all the bonds in the starting material(s) and of those in the likely products of decomposition or reaction, rather than on the group contribution methods used with computer programs, which are more accurate but... 

OR if its exothermic energy >500 J/g and onset below 500°C, then it must undergo DoT series one testing. 

Weis et al. (2003) cite an exothermic energy release upon pyrite oxidation of 1409kJ/mol pyrite, equating to 11.7 kJ/g pyrite. Of course, the rate of release of heat in kW from a waste tip will depend on physicochemical factors such as grain size (exposed surface area), permeability of the mass to O2, and also on the activity of the bacteria that catalyse the redox reactions involving Fe and S. 

Combustion is an oxidation-reduction reaction between a nonmetallic material and molecular oxygen. Combustion reactions are characteristically exothermic (energy releasing). A violent combustion reaction is the formation of water from hydrogen and oxygen. As discussed in Section 9.5, the energy from this reaction is used to power rockets into space. More common examples of combustion include the burning of wood and fossil fuels. The combustion of these and other carbon-based chemicals forms carbon dioxide and water. Consider, for example, the combustion of methane, the major component of natural gas ... 

Figure 28.15, curve a, displays the emission spectrum. Anthracene (An) can be added to this system without electrochemical interference, yet it alters the spectrum to the anthracene-like distribution of Figure 28.15, curve b. Apparently, the exothermic energy transfer... 

In contrast to the electron transfer reactions in question, the efficiency of which is primarily determined by the difference of redox potentials of the excited donor molecule and the acceptor and, hence, by the variation in free energy (21), efficiencies of exothermic energy transfers depend solely on the local concentration of an appropriate quencher. 

In this reaction, water from the solid (s) gypsum is released in gas (g) form. It is an endothermic reaction (energy is absorbed). The reverse reaction, in which liquid (1) water is added to the plaster of Paris, is exothermic (energy is released) ... 

For most elements, the first electron gained is exothermic (energy given off). Chlorine s electron affinity (E.A.) is —349 kJ per mole of electrons gained. The higher the first electron affinity (chlorine s is high), the more likely the element is to form an anion. The electron affinities of the elements display loose trends to increase in a period with the atomic number. 

Producer gas is manufactured by passing air and steam through a bed of hot coal or coke at a temperature of 980 to 1540°C, depending on the fusion points of the fuel ash. The primary purpose of the steam (25 to 30 % of the weight of the coke) is to employ the exothermic energy from the reaction between carbon and oxygen to supply energy (heat) to the endothermic carbon-steam reaction. 

Note that ASsurr is positive, as expected, since this reaction is exothermic energy flows to the surroundings as heat, increasing the randomness of the surroundings. 

In contrast to what is usually observed in organic photochemistry, exothermic energy transfer involving transition metal complexes does not always occur at diffusion controlled rates (204). Several investigations employing well-characterized aromatic triplet donors and organometallic acceptors have been aimed at elucidating the factors that affect the efficiencies... 

The exothermic energy region is best attained using excited reactants (see 13.4). 

---