40. Solution to Chemistry Problem

34.3 When determining the copper content in aviation fuels by the "standard addition method", 50.0 cm3 of the analyzed solution was added to each of four 500.0 cm3 measuring flasks, and 1.0; 5.0 and 10.0 cm3 of a standard solution with a concentration of 5 μg copper in 25 cm3 were added to the second, third and fourth, respectively. The volumes of the solutions in the measuring flasks were brought up to the mark with distilled water. The atomic absorption of these solutions was 7; 35 and 70 units, respectively. Determine the copper concentration in the analyzed solution (in mg/dm3) by calculation and graphical methods.