Reaction, spontaneous

Effect of Temperature, Pressure, and Concentration on Reaction Spontaneity... 

AH, the change in enthalpy (Chapter 8) a negative value of AH tends to make a reaction spontaneous. 

EFFECT OF TEMPERATURE. PRESSURE. AND CONCENTRATION ON REACTION SPONTANEITY... 

One of the most important characteristics of a cell is its voltage, which is a measure of reaction spontaneity. Cell voltages depend on the nature of the half-reactions occurring at the electrodes (Section 18.2) and on the concentrations of species involved (Section 18.4). From the voltage measured at standard concentrations, it is possible to calculate the standard free energy change and the equilibrium constant (Section 18.3) of the reaction involved. 

As pointed out previously, the value of the standard cell voltage, E°, is a measure of the spontaneity of a cell reaction. In Chapter 17, we showed that the standard free energy change, AG°, is a general criterion for reaction spontaneity. As you might suppose, these two quantities have a simple relation to one another and to the equilibrium constant, K, for the cell reaction. 

Determine E° and reaction spontaneity from standard potentials. 

Only one equilibrium constant for gas-phase reactions (Chapter 12), the thermodynamic constant K, often referred to as Kp. This simplifies not only the treatment of gaseous equilibrium, but also the discussion of reaction spontaneity (Chapter 17) and electrochemistry (Chapter 18). 

Self-Test 12.5B (a) Write the chemical equation for the reaction corresponding to the cell Hg(l) Hg2Cl2(s) HCl(aq) Hg2(NO )2(aq) Hg(l). (b) Given that the cell emf is reported as positive, is the cell reaction spontaneous as written ... 

We apply the condensed form of the seven-step strategy. We need to calculate a pressure that is Just sufficient to make the reaction spontaneous. That means solving for the pressure at which A G = 0,... 

C14-0076. Without doing any calculations, answer the following for the formation of NO2 from N2 and O2, and state your reasons (a) Is there any temperature at which the reaction is spontaneous when all reagents are at 1 bar pressure (b) At 298 K, is there any combination of partial pressures of the reagents that would make the reaction spontaneous ... 

TABLE 6.1 HOW CHANGES IN ENTHALPY AND ENTROPY AFFECT REACTION SPONTANEITY ... 

Which of the following is NOT a variable in the Gibbs free energy equation, which determines reaction spontaneity ... 

Gas-phase ion chemistry is a broad field which has many applications and which encompasses various branches of chemistry and physics. An application that draws together many of these branches is the synthesis of molecules in interstellar clouds (Herbst). This was part of the motivation for studies on the neutralization of ions by electrons (Johnsen and Mitchell) and on isomerization in ion-neutral associations (Adams and Fisher). The results of investigations of particular aspects of ion dynamics are presented in these association studies, in studies of the intermediates of binary ion-molecule Sn2 reactions (Hase, Wang, and Peslherbe), and in those of excited states of ions and their associated neutrals (Richard, Lu, Walker, and Weisshaar). Solvation in ion-molecule reactions is discussed (Castleman) and extended to include multiply charged ions by the application of electrospray techniques (Klassen, Ho, Blades, and Kebarle). These studies also provide a wealth of information on reaction thermodynamics which is critical in determining reaction spontaneity and availability of reaction channels. More focused studies relating to the ionization process and its nature are presented in the final chapter (Harland and Vallance). 

All of these reagents also undergo reaction spontaneously with acyl halides to generate the corresponding acyl-phosphoryl products (Figure 3.4). Reaction is easily accomplished by the slow addition of the acyl halide to the stirred phosphorus reagent, upon which an exothermic reaction ensues. This approach has been extensively exploited for the preparation of a wide range of a-ketophospho-nates.31-52... 

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