To determine the concentration of copper II ions in a solution using colorimetry, follow these steps:1. Prepare a series of standard solutions: Create a series of standard solutions with known concentrations of copper II ions. You can do this by diluting a stock solution of copper II sulfate to various concentrations e.g., 0.1 M, 0.05 M, 0.025 M, 0.0125 M, and 0.00625 M .2. Complex formation: Copper II ions in solution have a blue color, but the intensity of the color may not be directly proportional to the concentration. To improve the accuracy of the colorimetric analysis, add a reagent that forms a colored complex with copper II ions. A common reagent for this purpose is ammonium hydroxide, which forms a deep blue complex with copper II ions called tetraamminecopper II complex.3. Measure the absorbance: Use a colorimeter or a spectrophotometer to measure the absorbance of each standard solution at the wavelength of maximum absorbance usually around 600-700 nm for the tetraamminecopper II complex . Make sure to zero the instrument with a blank solution a solution without copper II ions but containing the complexing reagent .4. Create a calibration curve: Plot the absorbance values of the standard solutions against their respective concentrations. The resulting graph should be a straight line, which represents the relationship between absorbance and concentration for the copper II complex. This is called the calibration curve.5. Analyze the unknown solution: Add the complexing reagent ammonium hydroxide to the unknown copper II ion solution and measure its absorbance at the same wavelength used for the standard solutions.6. Determine the concentration: Use the calibration curve to determine the concentration of copper II ions in the unknown solution. Locate the absorbance value of the unknown solution on the y-axis of the calibration curve, and then find the corresponding concentration on the x-axis.By following these steps, you can accurately determine the concentration of copper II ions in a solution using colorimetry.