To determine the concentration of iron II ions in the original solution, the student should follow these steps:1. Prepare a series of standard solutions with known concentrations of iron II ions by dissolving known masses of iron II sulfate in water and diluting to known volumes. 2. Measure the absorbance of each standard solution using a colorimeter at a specific wavelength usually around 510 nm for iron II ions . Record the absorbance values.3. Plot a calibration curve by graphing the absorbance values y-axis against the known concentrations of iron II ions x-axis . The curve should be a straight line, and the equation of the line can be determined using linear regression y = mx + b, where m is the slope and b is the y-intercept .4. Measure the absorbance of the unknown sample using the colorimeter at the same wavelength as the standard solutions.5. Use the equation of the calibration curve to convert the absorbance of the unknown sample to concentration. For example, if the absorbance of the unknown sample is A, the concentration of iron II ions in the sample can be calculated as A - b / m.6. Calculate the percentage error of the experiment by comparing the experimental concentration of iron II ions to the theoretical concentration based on the known mass of iron II sulfate and the volume of the solution . The percentage error can be calculated as:Percentage error = |Experimental concentration - Theoretical concentration| / Theoretical concentration x 100%To improve the accuracy of the results, the student can:1. Use more accurate equipment, such as a spectrophotometer instead of a colorimeter, to measure absorbance.2. Increase the number of standard solutions to obtain a more accurate calibration curve.3. Ensure that all glassware and equipment are clean and free of contaminants.4. Use a more accurate method for weighing the iron II sulfate and for measuring the volumes of the solutions.5. Repeat the experiment multiple times and calculate the average concentration to minimize random errors.