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?
4 answers
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.
what is an ICE?
I - initial concentration
C - change in concentration
E - Equilibrium concentration
C - change in concentration
E - Equilibrium concentration
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
[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
4 answers