Equilibrium disturbances, effect

Rabbits (15-20/group) of unspecified strain and sex were exposed to 0 or 70,180 ppm leaded gasoline for 2 hours (Przybylowski 1971). All the exposed animals exhibited periods of restlessness, equilibrium disturbances, convulsions, and narcosis after 35 minutes. However, no histopathology of the brain tissue was conducted. These effects may have been partially due to the presumably low oxygen concentration in the exposure atmosphere, as discussed in Section 2.2.1.2, Cardiovascular Effects. 

If the pH is increased and (H+) approaches Ki the term Ki(H+) in equation (38) will begin to be of appreciable magnitude compared to (H+)a. However, with quinhydrone, other disturbing effects influence the results in alkaline solutions. The fact that quinone and hydro-quinone are in equilibrium with quinhydrone has been ignored in the development of equation (38). It has been discussed on page 199. Equation (3S) may be put in the form... 

These are both instances of what is known as active transport. Care must be taken to distinguish true active transport from certain other effects. For example, the concentration of Mg ions is much greater in most cells than in the surrounding fluid, This does not imply active transport, since the Mg " ions are strongly bound in the cells, a process which reduces the effective concentration of the ions and so disturbs the equilibrium. Another effect which can give a false impression of active transport is the Donnan equilibrium discussed in Section 7.6. We saw there that there can be an abnormal distribution of ions across a membrane because of the presence of large cations or anions to which the membrane is impermeable. 

Disturbance Effect on Equilibrium Position Effect on Value of K... 

The transition of a system from one state to another is called the process. The process consists of a sequence of nonequilibrium stages. If the relaxation time of the system is much less than the time of the external disturbing effects, the system will have enough time to reach equilibrium such a process consists of a sequence of equilibrium states (strictly speaking, it should be an indefinitely slow process). The process consisting of a continuous sequence of equilibrium states is referred to as the equilibrium or quasiequilibrium process. Thus only an indefinitely slow process can be equilibrium, although at a slow enough transformation, a real process can come nearer to equilibrium than a closed. 

The motion of particles in a fluid is best approached tlirough tire Boltzmaim transport equation, provided that the combination of internal and external perturbations does not substantially disturb the equilibrium. In otlier words, our starting point will be the statistical themiodynamic treatment above, and we will consider the effect of botli the internal and external fields. Let the chemical species in our fluid be distinguished by the Greek subscripts a,(3,.. . and let f (r, c,f)AV A be the number of molecules of type a located m... 

The observation that a system at equilibrium responds to a stress by reequilibrating in a manner that diminishes the stress, is formalized as Le Chatelier s principle. One of the most common stresses that we can apply to a reaction at equilibrium is to change the concentration of a reactant or product. We already have seen, in the case of sodium acetate and acetic acid, that adding a product to a reaction mixture at equilibrium converts a portion of the products to reactants. In this instance, we disturb the equilibrium by adding a product, and the stress is diminished by partially reacting the excess product. Adding acetic acid has the opposite effect, partially converting the excess acetic acid to acetate. 

Cambridge) and G. Porter (London) studies of extremely fast chemical reactions, effected by disturbing the equilibrium by means of very short pulses of energy. 

It is possible to use K to calculate the extent to which reaction occurs when an equilibrium is disturbed by adding or removing a product or reactant To show how this is done, consider the effect of adding hydrogen iodide to the HI-H2-I2 system (Example 12.7). 

Le Chatelier s principle A relation stating that when a system at equilibrium is disturbed it responds in such a way as to partially counteract that change, 337-338 buffers and, 385 compression effects, 339-340 expansion effects, 339-340 precipitation equilibrium, 442 reaction conditions, 348q temperature changes, 340 Lead, 2,501 Leclanch cell, 500 Leucine, 622t... 

Attempts to determine the equilibrium constant for Equation (60), applying the method proposed by Fialkov [313] for an AB2 = A+2B type interaction, provided values that defy physical logic. This means that the equilibrium in Equation (60) shifts almost completely to the left, and that it is also disturbed by A + B = AB type interactions [313], which, in this case, correspond to the interaction F" + TaFs = TaF6". Due to the improbability of the presence of TaF5 in the melts, it makes more sense to attribute the TaFg ions to the equilibrium described in Equation (61), which provides an analogical effect on the additive values of the property. 

The most widely used reference electrode, due to its ease of preparation and constancy of potential, is the calomel electrode. A calomel half-cell is one in which mercury and calomel [mercury(I) chloride] are covered with potassium chloride solution of definite concentration this may be 0.1 M, 1M, or saturated. These electrodes are referred to as the decimolar, the molar and the saturated calomel electrode (S.C.E.) and have the potentials, relative to the standard hydrogen electrode at 25 °C, of 0.3358,0.2824 and 0.2444 volt. Of these electrodes the S.C.E. is most commonly used, largely because of the suppressive effect of saturated potassium chloride solution on liquid junction potentials. However, this electrode suffers from the drawback that its potential varies rapidly with alteration in temperature owing to changes in the solubility of potassium chloride, and restoration of a stable potential may be slow owing to the disturbance of the calomel-potassium chloride equilibrium. The potentials of the decimolar and molar electrodes are less affected by change in temperature and are to be preferred in cases where accurate values of electrode potentials are required. The electrode reaction is... 

Three-spin effects arise when the nonequilibrium population of an enhanced spin itself acts to disturb the equilibrium of other spins nearby. For example, in a three-spin system, saturation of spin A alters the population of spin B from its equilibrium value by cross-relaxation with A. This change in turn disturbs the whole balance of relaxation at B, including its cross-relaxation with C, so that its population disturbance is ultimately transmitted also to C. This is the basic mechanism of indirect nOe, or the three-spin effect. 

Low exchange currents. When an electrode reaction is possible but its exchange current is low, the equilibrium potential is readily disturbed by external effects. Such an influence is exerted in particular by foreign components (contaminants), the reactions of which are superimposed on the basic reaction. 

Le Chatelier s principle demonstrates the effect of disturbances on chemical equilibrium. Le Chatelier s principle can also help predict whether or not disturbances will affect the equilibrium constant. None of these will affect the equilibrium constant EXCEPT the —... 

Although it is not an explanation, Le Chatelier s principle is used to predict the effect of changes in conditions on the position of equilibrium. One statement of Le Chatelier s principle is If a system in equilibrium is subjected to a change which disturbs the equilibrium, the system responds in such a way as to counteract the effect of the change . The factors that may change the position of an equilibrium are concentration, temperature and pressure. 

Le Chatelier discovered that if a chemical system at equilibrium is stressed (disturbed) it will reestablish equilibrium by shifting the rates of the reactions involved. This means that the amounts of the reactants and products will change, but the ratio will remain the same. One can stress the equilibrium in a number of ways changes in concentration, pressure, and temperature. However, a catalyst will have no effect on the equilibrium amounts since it affects both the forward and reverse reactions equally. It will simply allow the reaction to reach equilibrium faster. 

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