Question

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 0.550. If a trial's absorbance is measured to be 0.350 and its initial concentration of SCN– was 0.0010 M, the equilibrium concentration of SCN– will be?

Is there a formula? Or do I use beer's law?

Answer 1

Use Beer' law with the standard to find a in A=abc, then use the trial data to find c given A, a, and b. Then the equilibrium and ICE will tell you how much SCN^- is at equilibrium.

Answer 2

what is an ICE?

Answer 3

I - initial concentration
C - change in concentration
E - Equilibrium concentration

Answer 4

actually, you don't need ICE at all.
[FeNCS^2+]=A(eq)/A(std)*.0002

Plug in the absorbances and find [FeNCS^2+].

After that subtract [FeNCS^2+] from the initial concentration of SCN-.

you should get 0.000873 M