In: Chemistry
Erioglucine is a bluecolored dye that absorbs its complementary color, red, in aqueous solution around 645 nm. Unfortunately, the local distilled water supply is consistently contaminated with a trace amount of a metal cation that also absorbs 645 nm light. Suppose then, a control sample of 0.0552 M erioglucine (aq; same water supply) has an absorbance of 0.331 and that a distilled water sample in a similar cuvette has an absorbance of 0.019. Determine the concentration of an erioglucine (aq) sample (same water supply) that has an absorbance of 0.237. Concentration: _____ M
According to Beer's law, absorbance (A) is as calculated as follow
A = c l
= molar absorptivity, c = concentration and l = length of sample tube
For a substance at two different concentration will remain same and l will be remain same.
Therefore we can write as A1/A2 = c1 /c2
A1 = 0.331 , c1 = 0.0552 and A2 = 0.237
From this equation unknown concentration can be calculated.
c2= c1 x A2 /A1 = 0.0552 x 0.237 / 0.331 = 0.0395 M