Determination of Equilibrium Constant

[MooCow]

I did an experiment in my Chem II class that required finding the equilibrium constant for this reaction

Fe3+ + SCN- ->Fe(SCN)2+

For the experiment, I had to use a calibration curve and Beer's law. How do I know that the calibration curve obeys Beer's law? I know that it would have to be a linear line, but are there other requirements?

To create this curve, I made solutions with Fe(NO3)3, KSCN, and HNO3. What would happen to the K value if I used water instead? Is it the acidity or the polarity that affects the equilibrium constant? How would I be able to increase or decrease a K value? Change the concentrations?

 

[symbolipoint]

For first part: straight-line, intersects the origin.

For second part: read your textbooks to properly study this, but if pH is decreased, formation constant will decrease; if increase the pH, then formation constant will increase.