A number of useful links related to equilibrium can be found on this website filed under chapter 16 for the honors course. (these parallel the materials in the AP)

Equilibrirum slide show 

 

ICE stands for "initial, change, and equilibrium", and general method for setting up chemistry problems which ask you to predict equilibrium concentrations from starting concentrations.  The following site provides an introduction and examples:

 

FeSCN (+2) equilibirium lab 

 

2009 class data:

Keq values:  229.72, 414, 100, 70, 0.3115, 67.04, 39.31, 77

 

 

(Feb 4, 2009 assignment) AP students:  after downloading and reading the lab linked above, answer the following questions.

1)   Write a complete ionic equation describing the reaction of interest in this lab activity.  (You'll have to think about this-- only the net ionic equation is given in the text.)

2)   If a solution has a %transmittance of 90%, what is its absorbance?  Is it less than or greater than the absorbance of a solution which transmits 50% at a given frequency?

3)  What is a complex ion?  What is the complex ion of interest in this lab?

4)  How are the standard solutions prepared in this lab?  How do you insure that the complex ion is pure, and not a mixture of complex with simpler decomposition products?

5)   How is the molar absorptivity coeffienct determined in this lab?  For which compound?  At what frequency?  At what wavelength?  In what units?

6)  What is the expression for the equilibrium constant in this lab activity?

7)  What is the value of the reaction quotient (Q) for a mixture of 5 mM potassium thiocyanate and 5 mM iron (III) nitrate, before any reaction has taken place?