Colorimetry is a technique used to determine the concentration of a colored compound in a solution by measuring the absorbance of light at a specific wavelength. In this case, we want to quantify the concentration of copper II ions in a water sample. To do this, we can follow these steps:1. Prepare a series of copper II ion standards: Prepare a stock solution of known concentration of copper II sulfate CuSO4 . Then, create a series of standard solutions with varying concentrations of copper II ions by diluting the stock solution with distilled water. For example, you can prepare 5 standard solutions with concentrations of 1, 2, 4, 6, and 8 ppm parts per million .2. Complex formation: Copper II ions in solution are not very colorful and do not strongly absorb visible light. To enhance the color and improve the sensitivity of the measurement, we can form a complex with a suitable ligand. One common ligand used for this purpose is ammonium hydroxide NH4OH . Add an equal volume of ammonium hydroxide to each standard solution and the water sample. This will form a deep blue complex called tetraamminecopper II complex [Cu NH3 4 H2O 2]2+.3. Measure absorbance: Using a colorimeter or a spectrophotometer, measure the absorbance of each standard solution and the water sample at the wavelength of maximum absorbance for the tetraamminecopper II complex, which is around 635 nm.4. Calibration curve: Plot a graph of absorbance y-axis against the concentration of copper II ions in ppm x-axis for the standard solutions. The graph should be a straight line, and this is called the calibration curve.5. Determine the concentration of copper II ions in the water sample: Locate the absorbance value of the water sample on the y-axis of the calibration curve. Draw a horizontal line from this point to intersect the calibration curve, and then draw a vertical line from this intersection point down to the x-axis. The value on the x-axis where this vertical line intersects is the concentration of copper II ions in the water sample.By following these steps, you can successfully quantify the concentration of copper II ions in a water sample using colorimetry.