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.

 

[quicknote]

As a scientist, it is important to ensure that the data and results obtained from experiments are accurate and reliable. In this case, the determination of equilibrium constant for the reaction Fe3+ + SCN- ->Fe(SCN)2+ requires the use of a calibration curve and Beer's law.

To answer your first question, there are certain requirements for a calibration curve to obey Beer's law. These include having a linear relationship between absorbance and concentration, using a single wavelength of light, and having a constant path length. Additionally, the concentration range used should be within the linear range of the instrument. If these requirements are met, then the calibration curve can be said to obey Beer's law.

In regards to using water instead of HNO3 in the solutions, this would not affect the equilibrium constant (K value) as long as the concentration of Fe3+ and SCN- remains the same. The equilibrium constant is a measure of the ratio of products to reactants at equilibrium and is not affected by the solvent used. However, the acidity of the solution can affect the equilibrium constant as it can change the concentration of ions in solution.

To increase or decrease the equilibrium constant, you can manipulate the concentrations of reactants and products. Increasing the concentration of reactants will shift the equilibrium towards the products, resulting in a higher equilibrium constant, and vice versa. However, it is important to note that changing the concentrations of reactants and products will also affect the reaction rate and may not always result in a significant change in the equilibrium constant.

In conclusion, the determination of equilibrium constant requires careful consideration of experimental conditions and accurate data analysis. By following the requirements for Beer's law and understanding the factors that can affect the equilibrium constant, you can ensure the reliability and accuracy of your results.