Question

What is the concentration of iron(II) sulfate in a sample of water taken from a lake, using spectrophotometry with a known molar absorptivity of 11,300 L/mol*cm, if the absorbance of the sample is measured to be 0.423 at a wavelength of 510 nm?

Answer 1

To calculate the concentration of iron II  sulfate in the sample, we can use the Beer-Lambert Law, which states:A =  * c * lwhere A is the absorbance,  is the molar absorptivity  L/mol*cm , c is the concentration  mol/L , and l is the path length  cm .In this case, we have:A = 0.423 = 11,300 L/mol*cml = 1 cm  assuming a standard cuvette We need to solve for c  the concentration :0.423 = 11,300 * c * 1Now, divide both sides by 11,300:c = 0.423 / 11,300c  0.0000374 mol/LSo, the concentration of iron II  sulfate in the sample is approximately 0.0000374 mol/L or 37.4 mol/L.