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Equilibrium State of a Reactive Liquid Phase

Equilibrium State of a Reactive Liquid Phase. For reactions occurring in a liquid phase, our equilibrium expression holds:

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Equilibrium State of a Reactive Liquid Phase

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  1. Equilibrium State of a Reactive Liquid Phase • For reactions occurring in a liquid phase, our equilibrium expression holds: • The reference state for liquid-phase reactants is the pure component at the reaction temperature, a pressure of 1 bar, in the liquid state. Check the table in Appendix C. • The activity of each component in the liquid can be expressed in terms of fugacity: • where xi is the mole fraction of i, gi is the activity coefficient and fil is the pure component liquid fugacity of species i. What happens to fil and fio ?

  2. Equilibrium State of a Reactive Liquid Phase • If we ignore the effect of pressure on the fugacity of a pure liquid, the expression for the activity of a species simplifies to: • 1 • and our governing equation for the equilibrium state of a liquid phase reaction becomes: • 13.32 • We often use concentrations (mole/litre) in the place of activities. This assumes that the liquid mixture is ideal (all activity coefficients are unity) and the volume of the liquid does not change. This is rarely the case.

  3. Equilibrium State of a Reactive Liquid Phase • Consider the following reaction which occurs in the liquid phase: • (MeOH) (IB) (MTBE) • We determine the equilibrium constant, K, from the Gibbs energies of the pure components in the liquid state at the reaction temperature and 1 bar pressure. • This equilibrium constant relates to the liquid phase activities by:

  4. Equilibrium State of a Reactive Liquid Phase • We can relate the mole fractions of the system components to the reaction extent: • 13.5 • where, • In our case, • Substitution of these mole fractions allows us to calculate the reaction extent from the equilibrium constant relation.

  5. Equilibrium State of a Reactive Liquid Phase • Recall, • where gi is a function of xMeOH, xIB, xMBTE and temperature. • Solving the above equation in terms of e can be achieved by successive substitution or trial and error. • Let’s list all of the equations and unknowns we would need to solve for and make a plan to solve the equations in Excel. What information would we need? • What can we do so far?What other problems would we like to be able to tackle?

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