To determine the concentration of iron ions in a sample of tap water using spectrophotometry, you will need to follow these steps:1. Collect a sample of tap water.2. Prepare a series of standard solutions containing known concentrations of iron ions. You can use a standard iron solution e.g., 1000 ppm Fe and dilute it to create a range of concentrations e.g., 0.5, 1, 2, 5, and 10 ppm .3. Measure the absorbance of each standard solution at the wavelength that corresponds to the maximum absorbance of the iron complex usually around 510 nm for the Fe-phenanthroline complex . Record the absorbance values.4. Create a calibration curve by plotting the absorbance values y-axis against the known concentrations of iron ions x-axis . Fit a linear regression line to the data points.5. Treat the tap water sample with a suitable reagent to form a colored complex with iron ions. For example, you can use 1,10-phenanthroline, which forms a red-orange complex with Fe II ions. Make sure to adjust the pH of the sample to the optimal range for complex formation usually around pH 3-4 .6. Measure the absorbance of the treated tap water sample at the same wavelength used for the standard solutions around 510 nm .7. Use the calibration curve to determine the concentration of iron ions in the tap water sample. Locate the absorbance value of the sample on the y-axis, and find the corresponding concentration on the x-axis.8. Report the concentration of iron ions in the tap water sample.Keep in mind that this is a general procedure, and specific details may vary depending on the equipment and reagents used. Always follow the manufacturer's instructions and safety guidelines when working with chemicals and equipment.