Monday, 14 October 2013

7. Chemical Equilibrium
Chemical equilibrium can be described as the final composition of the reaction mixture.
Some reactions are irreversible (Reaction proceeds from reactants to products and cannot go back to original form).

There is always a limiting reactant (the reactant that’s concentration when zero stops the reaction). Some reactions can be reversible (product can be reversed back into reactants).
 To see if your reaction has reached equilibrium you can always calculate the equilibrium constant with the formula  ((product 1)(prpduct2))/(reactant1)(reactant2)) =K
 where it would be displayed in a reaction as reactant 1 + reactant 2 = product 1 + product 2. The stoichiometry would be displayed as exponents in the formula.  

When ratio=K
According to the law of mass action, there is no shifting of reaction and there will be no change in the concentration of reactants and products and the system is already at equilibrium.
When ratio> K
                             
In this condition the reaction will shift in the backward direction to achieve equilibrium state. At equilibrium quantity of product will decrease and the quantity of reactants will increase.
When ratio<K
In this condition the reaction will shift in forward direction to achieve equilibrium state. At equilibrium quantity of product will increase and the quantity of reactants will decrease.
All mole fractions can be expressed as a single variably (extent of reaction at equilibrium ξ).
Extent of reaction is a way to determine unknown molar flow rates for a reactive process.
http://www.google.co.za/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&ved=0CDsQtwIwAg&url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Djyso8NSytWw&ei=z6laUpazDOe50QWmroCgBg&usg=AFQjCNHB7CMRV114NHKA5VEJlQWByVSWZA&sig2=oBYEPudNZxWEhMvOHFwo8Q&bvm=bv.53899372,d.d2k
The degree of freedom analysis follows as:

Number unknown labeled variables + number independent reactions – number independent reactive species –number independent nonreactive species – number other equations relating unknown variables = number of degrees of freedom 

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