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 0.500. If a trial's absorbance is measured to be 0.310 and its initial concentration of SCN– was 0.0010 M, the equilibrium concentration of SCN– will be

Answer 1

A very similar question was posted and answered here:
http://Jiskha.com/display.cgi?id=1218235719
Check it out for the method used. It is the same as your question. Only the numbers are slightly different.

Answer 2

thanks!