Question

What is the concentration of iron (Fe) in a sample of river water using spectrophotometry at a wavelength of 510 nm? Given that the absorbance value of the sample at 510 nm is 0.42, and the molar absorptivity of iron (Fe) at that wavelength is 18,000 M^-1 cm^-1.

Answer 1

To calculate the concentration of iron  Fe  in the sample, we can use the Beer-Lambert Law, which states:A =  * c * lwhere A is the absorbance,  is the molar absorptivity, c is the concentration, and l is the path length  usually in cm .In this case, we have:A = 0.42 = 18,000 M^-1 cm^-1l = 1 cm  assuming the standard path length We need to solve for c  the concentration of iron :0.42 = 18,000 * c * 1Now, divide both sides by 18,000:c = 0.42 / 18,000c  0.0000233 MSo, the concentration of iron  Fe  in the sample of river water is approximately 0.0000233 M or 23.3 M.