80. Solving a chemistry problem

2. The CuSO4 solution obtained after processing the sample of slag (m=2 g) was transferred into a flask with a capacity of 100 ml, ammonia solution and water were added to it up to the mark. A series of standards was prepared from five solutions containing 1.0; 2.0; 3.0; 4.0 and 5.0 mmol/L Cu. With the same layer thickness, the color intensity of the sample solution coincided with the color of the third standard solution. Calculate the percentage of copper in the slag.