chem
posted by anonymous .
The standard solution of FeSCN2+ (prepared by combining 9.00 mL of 0.200 M Fe(NO3)3 w/1.00 mL of 0.0020 M KSCN) has an absorbance of 0.520.
If a trial's absorbance is measured to be 0.275 and its initial concentration of SCN– was 0.00060 M, what is the equilibrium concentration of SCN–?

Use the standard solution to calculate the constant a in Beer's Law of A = abc. You know A, b(the cell length) and c the concn.
Then the same A= abc to calculate concn from the unknown. You have A, you have calculated a from above, you have b and can calculate c, the concn of the unknown. You know how much SCN^ you started with the difference should be how muuch is left. you started with so