Beer Lambert Law Graph
When measuring the absorbance of the solutions, why are the measures taken to increase the concentration?
One of the experiments I have to do is "The Beer Lambert law" – Spectroscopy. Where do I have to measure the absorbance of standard solutions of complex ferroin. I would also like to know: 1) how I can calculate the concentration of iron in absorbance? 2) Ater, drawing a graph of absorbance vs. concentration (For samples of known concentration), how can then calculate the molar absorptivity at 470 nm ferroin? 3) How I can use the chart below to establish the total mass of iron in the toether the tablet with the estimated errors? 4) What color of light corresponds to 470 nm, and why this wavelength was chosen for this experiment? ps [I'm sorry for asking questions to both - is that I can find no adequate response, and my teachers do not help me!] Thanks to anyone who can help me out.
Well, you know the law: A = E * d * C are using the same cuvette for all measurements, so when you change the solution You can measure there is the possibility that some amount of the previous solution will remain in the bucket. If the above solution is more concentrated, the error will be great, and to change much the actual concentration of the new solution in the bucket. If it is less concentrated than the error will be small. To answer (1) with do (2) first. Since you want to E470, which should be measuring the absorbance of standards at 470 nm. You make the plot. So the method of least squares to find the equation describing the standard curve (linear). The slope you find is E * d. d depends on your tank and is usually 1 cm = E slope and given in the respective unit. Once that equation is used to calculate the concentration of ferroin of an unknown on the basis of the absorbance. A Thereafter you have to find the relationship between iron and ferroin (stoichiometry is 1:1?) So you can find the iron concentration for the mass, I do not know exactly the experimental procedure, but once the concentration of iron just have to do some calculations (depending on the experimental constitution) and calculate. As to 4, usually by choosing wavelengths where the absorbance is maximum (peak in the spectrum). I do not know if there is another reason (eg you have other substances in the sample whose spectra overlap with that of ferroin at some wavelengths, but not significantly to 470 nm, even in this case should ferroin have a peak at or near 470 nm) The color which corresponds to 470 nm can definitely be found on the web