To determine the concentration of iron II in a water sample collected from a local river using colorimetry, you will need to follow these steps:1. Collect a water sample from the local river.2. Prepare a series of standard solutions with known concentrations of iron II ions. This can be done by dissolving a known amount of iron II salt, such as ferrous sulfate FeSO4 , in a known volume of water.3. Treat both the water sample and the standard solutions with a colorimetric reagent that specifically reacts with iron II ions to produce a colored complex. A common reagent for this purpose is 1,10-phenanthroline, which forms a red-orange complex with iron II ions.4. Measure the absorbance of the colored complex in each standard solution and the water sample using a spectrophotometer. The absorbance is directly proportional to the concentration of iron II ions in the solution, according to the Beer-Lambert law.5. Plot a calibration curve by graphing the absorbance values of the standard solutions against their known iron II concentrations. The curve should be linear, and its equation can be determined by performing a linear regression analysis.6. Use the equation of the calibration curve to determine the concentration of iron II ions in the water sample. Simply plug the absorbance value of the water sample into the equation and solve for the concentration.7. Report the concentration of iron II ions in the water sample, typically in units of mg/L or ppm parts per million .Keep in mind that this is a general outline of the procedure, and specific details may vary depending on the equipment and reagents used. It is essential to follow proper laboratory techniques and safety protocols throughout the process.