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How can I determine the reaction order of the reaction acetylsalicylic acid + water to salicylic acid + acetic acid with use of a spectrophotometer?

I thought of measuring the absorbance spectrum of both substances individually, compare the 2 spectra, and then look at which wavelength the absorbance of acetylsalicylic acid exists whereas the absorbance of salicylic acid at that wavelength is negligible.

Lastly, use that wavelength to calculate concentrations of acetylsalicylic acid at certain time intervals and conclude the reaction order out of the change in concentration vs time. (for example making a graph on Excel for Concentration vs time -> linear = 0 order, exponential = 1st order)

Is this possible or am I thinking too hard/easy? Is there any other other way?

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I think your reasoning is sound. However, a factor you may need to take into account is that you have a number of possible related species here, each of which has a different UV absorbance spectrum. You have acetylsalicylic acid, acetylsalicylate anion, salicylic acid, salicylate anion, and salicylate dianion (this one will probably have a markedly different UV spectrum from the others). The relative amounts of these species present would be affected by pH, so it would be important to buffer the reaction solution, to maintain constant pH.

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