Posted by Sara on .
Hi
Please help
Initial [Fe3+] = 0.00050 M
Initial [SCN] = 0.0010 M
Equilibrium [Fe(SCN)2+] = 5.7 x 105
Find [Fe3+]E and [SCN]E (in mol/L)
Find K.
Balanced equation is:
Fe3+ + SCN > Fe(SCN)2+ (reversible)
I know I can get K if I have the equilibrium concentrations, but not sure how to calculate these with so little info.
Thanks.

Chemistry 
DrBob222,
...........Fe^+3 + SCN^ ==> FeSCN^+2
begin......5E4....1E3......0
change
equilib......................5.7E5
Wouldn't you think that if the equilibrium concn FeSCN^+2 = 5.7E5 and it was zero initially, then 5.7E5 M must have been used from the initial SCN^ of 1E3 and 5.7E5 must have been used from the initial 5E4 of Fe^+3.
So equilibrium concn Fe^+3 is 5E4  5.7E5 and equilibrium concn SCN^ is 1E3  5.7E5. Check for typos