To determine the concentration of iron II ions in the water sample, we can use the Beer-Lambert Law, which states that the absorbance A of a solution is directly proportional to its concentration c and the path length l of the cuvette used in the colorimeter:A = clWhere is the molar absorptivity also known as the molar absorption coefficient of the iron II ions at 510 nm.First, we need to determine the molar absorptivity of the iron II ions in the standard solution. To do this, we need to know the absorbance of the standard solution at 510 nm. Let's assume that the absorbance of the standard solution is A_standard.Next, we can use the Beer-Lambert Law to find the molar absorptivity: = A_standard / c_standard * l Where c_standard is the concentration of the standard solution 4.65 x 10^-5 M and l is the path length of the cuvette usually 1 cm .Once we have the molar absorptivity, we can use the Beer-Lambert Law again to find the concentration of iron II ions in the water sample:c_sample = A_sample / * l Where A_sample is the absorbance of the water sample 0.55 and and l are the same as before.Without the absorbance of the standard solution A_standard , we cannot calculate the exact concentration of iron II ions in the water sample. However, if you provide the absorbance of the standard solution, we can use the above equations to find the concentration of iron II ions in the water sample.