To determine the concentration of the copper II sulfate solution, we need to use the standard calibration curve. A calibration curve is a graph that shows the relationship between the concentration of a substance and its absorbance value. First, you need to prepare a series of standard solutions with known concentrations of copper II sulfate and measure their absorbance values at 620 nm. For example, you can prepare solutions with concentrations of 0.1, 0.2, 0.3, 0.4, and 0.5 M or any other suitable range and measure their absorbance values.Next, plot the absorbance values y-axis against the concentrations x-axis on a graph. The resulting graph should be a straight line, as the relationship between concentration and absorbance follows the Beer-Lambert law: A = cl, where A is absorbance, is the molar absorptivity, c is the concentration, and l is the path length of the cuvette.Once you have the calibration curve, you can use the absorbance value of the unknown solution 0.45 to find its concentration. Locate the absorbance value of 0.45 on the y-axis and draw a horizontal line until it intersects the calibration curve. From this intersection point, draw a vertical line down to the x-axis, which will give you the concentration of the unknown solution.Without the actual calibration curve data, I cannot provide the exact concentration of the copper II sulfate solution. However, by following the steps above and using your own calibration curve, you should be able to determine the concentration of the unknown solution.