Equilibrium/equilibria changes

Transient, or time-resolved, techniques measure tire response of a substance after a rapid perturbation. A swift kick can be provided by any means tliat suddenly moves tire system away from equilibrium—a change in reactant concentration, for instance, or tire photodissociation of a chemical bond. Kinetic properties such as rate constants and amplitudes of chemical reactions or transfonnations of physical state taking place in a material are tlien detennined by measuring tire time course of relaxation to some, possibly new, equilibrium state. Detennining how tire kinetic rate constants vary witli temperature can further yield infonnation about tire tliennodynamic properties (activation entlialpies and entropies) of transition states, tire exceedingly ephemeral species tliat he between reactants, intennediates and products in a chemical reaction. 

It follows that the position of thermodynamic equilibrium will change along the reactor for those reactions in which a change of tire number of gaseous molecules occurs, and therefore that the degree of completion and heat production or absorption of the reaction will also vaty. This is why the external control of the independent container temperature and the particle size of the catalyst are important factors in reactor design. 

The term balance means that all forces generated by, or acting on, the rotating element of a machine-train are in a state of equilibrium. Any change in this state of equilibrium creates an imbalance. In the global sense, imbalance is one of the most common abnormal vibration profiles exhibited by all process machinery. 

The equilibrium constant for this system, like all equilibrium constants, changes with temperature. At 100°C, K far the N204-N02 system is 11 at 150°C, it has a different value, about 110. Any mixture of N02 and N204 at 100°C will react in such a way that the ratio (Eno /EnjO, becomes equal to 11. At 150°C, reaction occurs until this ratio becomes 110. 

Example 12.4 illustrates a principle that you will find very useful in solving equilibrium problems throughout this (and later) chapters. As a system approaches equilibrium, changes in partial pressures of reactants and products—like changes in molar amounts—are related to one another through the coefficients of the balanced equation. 

Figure 9-1 shows the addition of solid iodine to a mixture of water and alcohol. At first the liquid is colorless but very quickly a reddish color appears near the solid. Stirring the liquid causes swirls of the reddish color to move out— solid iodine is dissolving to become part of the liquid. Changes are evident the liquid takes on an increasing color and the pieces of solid iodine diminish in size as time passes. Finally, however, the color stops changing (see Figure 9-1). Solid is still present but the pieces of iodine no longer diminish in size. Since we can detect no more evidence of change, we say that the system is at equilibrium. Equilibrium is characterized by constancy of macroscopic properties ...

What happens if the road becomes smoother The jostling up reaction is less favored—the equilibrium conditions change in favor of the golf balls at the lower level. 

The prediction and understanding of a state of equilibrium constitutes one of the most important applications of thermodynamics. If we wait long enough, a system consisting of subsystems that are not at equilibrium will change until equilibrium is established. Heat will flow until all parts of the system are at the same temperature. Thus = = 7, is a criterion for equilibrium. 

A pressure displacement dp and a temperature displacement d T are made on the system. This causes changes in the chemical potentials dp,, and dp / If the phases are to remain in equilibrium, these changes must be equal so that... 

Example 8.2 Use Figure 8.9 to predict the phase changes that would occur when solid Sn at p = 0.1 MPa is compressed isothermally to p = 15 GPa at (a) 7 = 600 K (b) 7 = 550 K and (c) 7 = 250 K. Assume that the equilibrium phase changes occur rapidly enough to keep up with the change in pressure. 

The system CrO / Cx20 -, provided students with a new context within which to use the model previously created for the system NO2/N2O4. From this second system students (i) acquired additional evidence about the coexistence of reactants and products in a chemical reaction and (ii) could observe what happened when the equilibrium was changed. This last set of empirical evidence was included in the teaching activities specifically to support the testing of students previous models. 

In Study 8. Ic we examined how the reactant concentrations affected the forward reaction rate, but we have not yet examined how such a change influences the equilibrium condition. Change the initial concentrations to [A]o = 700 cells... 

Adding some steam to a reactor that is at chemical equilibrium changes the value of Q, so the reaction is no longer at equilibrium. The reaction proceeds in the direction that consumes some of the added reagent in order to reestablish equilibrium. 

C16-0041. Use your own words to define (a) initial concentrations, (b) change to equilibrium, (c) change to completion, and (d) equilibrium concentrations. 

Martinek et al. [28] defined the apparent reaction equilibrium in a biphasic system by the constant A),i. In their model, the ratio represents the equilibrium change when... 

Therefore, the activation energy of quasi-equilibrium conductivity changes as a logarithm of concentration of adsorption particles which, when the linear dependence between Nt and P is available, corresponds to situation observed in experiment [155]. We should note that due to small value m function (1.91) satisfactorily approximates the kinetics oit) A - B n(i + t/t>) observed in experiments [51, 167, 168]. Moreover, substantially high partial pressures of acceptor gas, i.e. at high concentrations of Nt expression (1.81) acquires the shape ait) Oait/toc) it,Nty " when t>toc>. This suggests that for... 

The method of representing the equilibrium state The value of the equilibrium constant changes if the reversible reaction is considered to proceed in the reverse direction. For example, the reaction A + B C + D can also be written asC + D A+Bso that [A] [B]/[C] [D] = kr/kf = K. In this case the value of the equilibrium constant for the reverse reaction is given by K = 1/K. To avoid such confusion while applying the law of mass action, the concentrations of the products are always placed in the numerator and those of the reactants in the denominator. 

The body s normal daily sodium requirement is 1.0 to 1.5 mEq/kg (80 to 130 mEq, which is 80 to 130 mmol) to maintain a normal serum sodium concentration of 136 to 145 mEq/L (136 to 145 mmol/L).15 Sodium is the predominant cation of the ECF and largely determines ECF volume. Sodium is also the primary factor in establishing the osmotic pressure relationship between the ICF and ECF. All body fluids are in osmotic equilibrium and changes in serum sodium concentration are associated with shifts of water into and out of body fluid compartments. When sodium is added to the intravascular fluid compartment, fluid is pulled intravascularly from the interstitial fluid and the ICF until osmotic balance is restored. As such, a patient s measured sodium level should not be viewed as an index of sodium need because this parameter reflects the balance between total body sodium content and TBW. Disturbances in the sodium level most often represent disturbances of TBW. Sodium imbalances cannot be properly assessed without first assessing the body fluid status. 

When setting the conditions in chemical reactors, equilibrium conversion will be a major consideration for reversible reactions. The equilibrium constant Ka is only a function of temperature, and Equation 6.19 provides the quantitative relationship. However, pressure change and change in concentration can be used to shift the equilibrium by changing the activities in the equilibrium constant, as will be seen later. 

By contrast with nonazeotropic systems, for azeotropic systems there is a maximum reflux ratio above which the separation deteriorates16. This is because an increase in reflux ratio results in two competing effects. Firstly, as in nonazeotropic distillation, the relative position of the operating surface relative to the equilibrium surface changes to improve the separation. This is countered by a reduction in the entrainer concentration, owing to dilution by the increased reflux, which results in a reduction in the relative volatility between the azeotropic components, leading to a poorer separation16. 

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