To determine the concentration of an unknown substance in a solution using colorimetry and a calibration curve, follow these steps:1. Prepare a series of standard solutions: Create a set of standard solutions with known concentrations of the substance of interest. These solutions will be used to create a calibration curve, which will help determine the concentration of the unknown substance.2. Measure the absorbance of the standard solutions: Using a colorimeter or a spectrophotometer, measure the absorbance of each standard solution at a specific wavelength. The wavelength should be chosen based on the maximum absorbance of the substance, which can be found in the literature or by scanning the absorbance spectrum of the substance.3. Plot the calibration curve: Create a graph with the absorbance values on the y-axis and the concentrations of the standard solutions on the x-axis. Fit a linear regression line to the data points, which will represent the calibration curve. The equation of this line will be used to determine the concentration of the unknown substance.4. Measure the absorbance of the unknown solution: Using the same wavelength as in step 2, measure the absorbance of the unknown solution.5. Determine the concentration of the unknown substance: Using the equation of the calibration curve, calculate the concentration of the unknown substance in the solution. To do this, substitute the absorbance value of the unknown solution into the equation and solve for the concentration x-value .For example, if the equation of the calibration curve is y = mx + b, where y is the absorbance, x is the concentration, m is the slope, and b is the y-intercept, then:x = y - b / mBy plugging in the absorbance value of the unknown solution y and using the slope m and y-intercept b values from the calibration curve, you can calculate the concentration x of the unknown substance in the solution.