Thursday 22 March 2012

Calculating Keq

Keq expresses the relative concentrations of reactants and products in an equilibrium. This is the equilibrium constant. Keq can be calculated as follows :



The [ ] represent the concentration in moles/L

If the molecules in the reaction have coefficients, these will become exponents for the molecules in the Keq formula. For example, if 2A + B <----> C + D the formula would look like this : Keq = [C][D] / [A]²[B]. Remember, this formula always calls for products OVER reactants.

Now, lets look at an example:                                

 2NO2 <--> N2O4

[N2O4] at equilibrium = 0.00140 M
[NO2] at equilibrium = 0.0172 M

Keq=[N2O4] / [NO2]²  
Keq=(0.00140)/(0.0172)²
Keq=4.73  


 

Wednesday 21 March 2012