100. Solving a chemistry problem

3. Place 10 ml of waste water into two 100 ml volumetric flasks. To the first flask was added 10 ml of a Cu(II) standard solution with a titer of 0.0010 g/ml. The required reagents were added to both flasks and diluted to the mark with water. The optical density of the solution from the first flask is 0.380, and from the second flask 0.240. Determine the concentration (g/l) of copper in wastewater. Answer: 0.171 g / l.