Post lab question for lab 4 the oxidation of a food dye by hypochlorite, the act
ID: 491336 • Letter: P
Question
Post lab question for lab 4 the oxidation of a food dye by hypochlorite, the active ingredient in household bleach. The reaction can be written as follows:
Dye(aq) + ClO-(aq)aproducts The rate law for this reaction is: Rate = k[ClO-]a[dye]b
1. If your reaction was first order with respect to [dye] then you will get the same slope regardless of whether or not you plot ln[dye] or ln(absorbance) vs. time. Why then do you think it is necessary to generate a Beer’s law plot? If necessary, look at the integrated form of a first order rate law to help you answer this question. ?
Explanation / Answer
The reason is that using the Beer's law would confirm the linearity of the reaction. Sometimes it may be the case that the reaction appears first order but the semi-log plot doesn't show the expected linearity, either due to the non-linearity of the photometer device itself, or because the molecules attain a non-homogeneous distribution. Beer's law test thus confirms the linearity.