4. Solution to Chemistry Problem

32. To prepare a standard solution of copper salt, from which, upon adding ammonia, 10 colored solutions were obtained, containing from 1.00 to 10.00 ml of the standard solution in 20 ml of water. Then 0.7500 g of the substance under study was dissolved in 250 ml of water. After the solution interacted with ammonia and diluted to 20 ml, its color intensity was equal to the intensity of 8 of the standard solution. Calculate the mass fraction of copper in the solution under study.