Question

To determine the % Cr in the chromium-complex Legna synthesized, she massed out a 1.0240 g sample of the Cr complex. She dissolved the sample in a volumetric flask and made 100.0 mL of solution. From the standard curve of Absorbance versus concentration Legna obtain [Cr^3+]=0.03933 M. Calculate the %Cr in the complex.

Answer 1

Concentration of Cr³⁺ in the 100 mL solution is 0.03933 M = 0.03933 mol/L

Volume of the solution = 100.0 mL = 0.1000 L

Hence, the total number of moles of Cr³⁺ in the solution can be calculated as

Molar mass of Cr = 51.9961 g/mol

Hence, the mass of Cr dissolved in the solution is

Note that a total of 1.0240 g of Cr complex was used to make the 100.0 mL solution.

Hence, the %Cr in the complex can be calculated as follows;

Hence, the percent Cr in the complex is approximately 19.97 %.