Question

What is the concentration of iron (II) ion in a sample of drinking water using colorimetry, if the absorbance of the sample is found to be 0.294 and the molar absorption coefficient of iron (II) complex is 10,500 M^-1 cm^-1 at the wavelength of 505 nm?

Answer 1

To find the concentration of iron  II  ion in the sample, we can use the Beer-Lambert Law, which states:A =  * c * lwhere A is the absorbance,  is the molar absorption coefficient, c is the concentration, and l is the path length  usually in cm .In this case, we have:A = 0.294 = 10,500 M^-1 cm^-1l = 1 cm  assuming the path length is 1 cm, which is a common value We need to solve for c  the concentration :0.294 = 10,500 * c * 1Now, divide both sides by 10,500:c = 0.294 / 10,500c  0.000028 MSo, the concentration of iron  II  ion in the sample is approximately 0.000028 M or 28 M.