Colorimetry is a technique used to determine the concentration of a colored compound in a solution by measuring its absorbance of light at a specific wavelength. To determine the concentration of nickel ions Ni2+ in a water sample using colorimetry, you can follow these steps:1. Preparation of the water sample: Filter the water sample to remove any suspended particles or impurities that may interfere with the colorimetric analysis.2. Complexation of nickel ions: Nickel ions in the water sample need to be converted into a colored complex that can be measured using a colorimeter or spectrophotometer. This can be achieved by adding a suitable complexing agent, such as dimethylglyoxime DMG . When DMG is added to the water sample, it reacts with the nickel ions to form a red-colored complex Ni DMG 2 . Ni2+ aq + 2 DMG aq Ni DMG 2 s 3. Calibration curve: Prepare a series of standard nickel solutions with known concentrations by diluting a stock nickel solution. Add the same amount of DMG to each standard solution as you did to the water sample. Measure the absorbance of each standard solution at the wavelength corresponding to the maximum absorbance of the Ni DMG 2 complex usually around 520 nm . Plot a calibration curve of absorbance versus nickel concentration.4. Measurement of the water sample: Measure the absorbance of the water sample containing the Ni DMG 2 complex at the same wavelength used for the calibration curve around 520 nm .5. Determination of nickel concentration: Using the calibration curve, find the concentration of nickel ions in the water sample by comparing its absorbance value to those of the standard solutions. This will give you the concentration of nickel ions in the water sample.6. Quality control: To ensure the accuracy of your results, it is recommended to perform replicate measurements of the water sample and to include a blank a sample without nickel ions in your analysis.By following these steps, you can determine the concentration of nickel ions in a water sample using colorimetry.