Question

What is the concentration of iron (Fe) present in a given water sample using colorimetry as the analytical method, given that the absorbance at a wavelength of 565 nm is 0.423 and the molar absorptivity of the Fe-phenanthroline complex is 11,100 M^-1 cm^-1?

Answer 1

To determine the concentration of iron  Fe  in the water sample, we can use the Beer-Lambert Law, which states:A =  * c * lwhere A is the absorbance,  is the molar absorptivity  M^-1 cm^-1 , c is the concentration  M , and l is the path length  cm .In this case, we have the absorbance  A = 0.423  and the molar absorptivity   = 11,100 M^-1 cm^-1 . We will assume the path length  l  is the standard 1 cm.Now we can solve for the concentration  c :0.423 = 11,100 * c * 1c = 0.423 / 11,100c  0.0000381 MSo, the concentration of iron  Fe  in the water sample is approximately 0.0000381 M or 38.1 M.