Question

Let's say that there are fingerprints or other type of dirt on the outside of the cuvette

A. What effect would this have on the %T readings? Why?

B. What effect would this have on the absorbance? Why?

C.Would this cause the reported equilibrium constant be too high or too low? Why?

Answer 1

A. Fingerprints or any other type of dirt on the cuvette would cause the %T readings to change. The %T readings are dependent on light passing through the cuvette. As compared to a clean cuvette, the presence of fingerprints or other dirt would affect how light passes through the cuvette, thus leading to a change in the %T readings. Although the specific effect would depend have to depend on the kind of dirt involved, most kinds of dirt, as well as fingerprints, would absorb and scatter light, typically leading to lower %T readings.

B.Absorbance is related to the %T through Beer's Law. If %T is changed as a result of fingerprints or dirt, then the absorbance would be changed too. Since fingerprints and most kinds of dirt absorb and scatter light, lessening the %T and increasing the absorbance.

C. The spectroscopic equilibrium experiment involving the formation of FeSCN²⁺, or thiocyanatoiron(III), in the reaction Fe³⁺(aq) + SCN