Question

What is the concentration of iron (II) ions in a water sample if the absorbance of the sample at a wavelength of 565 nm is measured to be 0.842 and it was found that a 1 cm cuvette contains 1.25 x 10^-4 moles of iron (II) ions? (The molar absorptivity of iron (II) ions at 565 nm is 1.9 x 10^4 L/mol cm).

Answer 1

To find the concentration of iron  II  ions in the water 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 of the solution, and l is the path length of the cuvette.We are given the following values:A = 0.842 = 1.9 x 10^4 L/mol cml = 1 cmWe need to find the concentration  c  of iron  II  ions in the water sample. Rearranging the Beer-Lambert Law equation to solve for c, we get:c = A /   * l Now, we can plug in the given values:c = 0.842 /  1.9 x 10^4 L/mol cm * 1 cm c = 0.842 / 1.9 x 10^4 L/molc = 4.4316 x 10^-5 mol/LTherefore, the concentration of iron  II  ions in the water sample is approximately 4.43 x 10^-5 mol/L.