A reaction mixture of 4.0 mL of 0.002 M SCN- and 5.0 mL of 0.002 M Fe3+ is diluted to 10.0 mL with 0.1 M HNO3 to form the blood-red FeNCS2+ complex. The equilibrium molar concentration of the FeNCS2+ determined from a standardization curve is 1.5x10^-4 mol/L. Calculate, in sequence, each of the following quantities in the aqueous solution to determine the equilibrium constant for the reaction:

Question

Fe3+(aq) + SCN-(aq) <--> FeNCS2+(aq)

A) moles of FeNCS2+ that form in reaching equilibrium

B) moles of Fe3+ that react to form the FeNCS2+ at equilibrium

C) moles of SCN- that react to form the FeNCS2+ at equilibrium

D) moles of Fe3+ initially placed in the reaction system

e) moles of SCN- initially placed un the reaction system

f) moles of FE3+ (unreacted) at equilibrium

G) moles of SCN- (unreacted) at equilibrium

h) molar concentration of Fe3+ (unreacted) at equilibrium

i) molar concentration of SCN- (unreacted) at equilibrium

j) molar concentration of FeNCS2+ at equilibrium

k) Kc = [FeNCS2+]/([Fe3+][SCN-])

Answer 1

I'll get you started.
mols SCN^- initially = M x L = ?
mols Fe^3+ initially = M x L = ?
(SCN^-) initially = 0.002 x 4/10 = 8E-4M
(Fe^3+) initially = 0.002 x 5/10 = 0.001M

.........Fe^3+ + SCN^- ==> FeNCS^2+
I.......8E-4.....1E-3........0
C........-x.......-x.........x
E......8E-4-x...1E-4-x......1.5E-4
So you know x is 1.5E-4 and that allows you to calculate values for (Fe^3+) and SCN^-) at equilibrium and that allows you to calculate Kc.
The rest of that question is busy work but when you want to answer a mol question, it is mols = M x L = ?