An unknown sample of Cu2+ gave an absorbance of 0.262 in an atomic absorption analysis. Then 1.00 mL of solution containing 100.0 ppm (= g/mL)Cu2+

An unknown sample of Cu2+ gave an absorbance of 0.262 in an atomic absorption analysis. Then 1.00 mL of solution containing 100.0 ppm (= μg/mL)Cu2+ was mixed with 95.0 mL of unknown, and the mixture was diluted to 100.0 mL in a volumetric flask. The absorbance of the new solution was 0.500.
(a) Denoting the initial, unknown concentration as [Cu2+]i, write an expression for the final concentration, [Cu2+ ]f, after dilution. Units of concentration are ppm.
(b) In a similar manner, write the final concentration of added standard Cu2+, designated as [S]f.
(c) Find [Cu2+]i in the unknown.