Chemical-engineering Students

Fugacity is supposed to be easily understood, especially because that was the main purpose of its invention. Lets just get some history straight first. In the beginning there was chemical potential, usually denoted as  μ, and defined as: Definition of Chemical Potential with G and n i being the Gibbs free energy and moles of compound i respectively. As you see  μ is used to describe the Gibbs free energy, and if you know thermodynamics you should know that Gibbs is used to describe chemical equilibrium in pure and mixed systems, if you didn't know, this is very important. The problem however with chemical potential is that it is an abstract concept, like the amount of honest bankers, in other words, it can not be directly measured. In its stead fugacity was invented by one, G.N. Lewis (Also famous for his Lewis dot structure of molecules and his mustache). G.N. Lewis Partial fugacity, is the pseudo-pressure exerted by the mixture of molecules in the vapor phase...

"Why can't a isothemal process be adiabatic?" This was the question my housemate, that studies geology and geography, asked me while studying for his thermodynamics test. As a chemical engineering student I was suppose to be able to answer him immediately, but it took me some pondering to give him a good answer. Lets consider the isothermal expansion of gas, and lets use the convention used by most thermodynamic textbooks that work (W) done by the system on the environment is said to be negative. Consider the diagram and the formula used for work done by isothermal expansion of an ideal gas and the heat formula. Isothermal expansion Work done by isothermal expansion of an ideal gas Heat formula for expansion of an ideal gas in a closed system And because, for reversible isothemal expansion the following is true: For reversible isothermal expansion  thus we can see that Q = -W, and W is not equal to 0 because the volume has changed, that mea...

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 ...

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: ...

I started this blog site for chemical engineering students all over the globe, as I am one myself, to be fun and to ask the stupid questions as well as teaching myself as I work on the blog site.