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Showing posts from June, 2012

Chemical Reaction Equilibrium hrxn as a function of T

I said in my previous post that I will discuss how to solve the equilibrium constant K when the enthalpy of the  reaction is not constant, but a function of temperature. That is to say: Enthalpy as a function of temperature If the above statement is true for the given system then you need to use the following, extremely long formula, I suggest doing this on excel or a similar program. To determine K T , the equilibrium constant at the new operating temperature,   use the following equation: K T when h rxn is a function of T The constants A, B, C, D and E you get from the heat capacities of the different elements in the chemical reaction with: The same goes for C, D and E From a previous post it is shown that v i is the stoichiometric coefficient of the reaction, remember that v i of the reactants are always negative and the products coefficients are always positive, this is really just convention more than anything else.  The nature ...

Chemical reaction equilibrium

When you are considering the chemical reaction equilibria, the equilibrium constant (K) obviously plays a major role in describing the kinetics of the reaction at the temperature being studied. That is what makes K such a useful parameter, telling a plant designer at an early stage if a chemical product will be formed or not. So how do you calculate K 2 , well its pretty straight forward: with K 1 the equilibrium constant at 298K and assuming hrxn is not a function of temperature, I'll discuss the method for determining K 2 when hrxn(T) in a later post, the reason for using K 1 at 298K  is that experimental data is regularly available for chemicals at this temperature: Enthalpy  chemical  i at 298K Gibbs energy of chemical i at 298K Thus using 298K values as your basis, and working from there. K 2 and T 2 values are the wanted equilibrium constant and the new temperature, respectively.  with: ...