Fe(NO3)3. 9H2O in 0.5M HNO3forms a colorless hexa-aquocomplex with the chemical formula{Fe(H2O)6}3+ (aq).
This complex can then undergo an equilibrium reaction withpotassium thiocynate (KSCN) to form a red complex with the chemicalformula {Fe(H2O)5SCN}2+ (aq). In order to make thisreaction occur, the two chemicals need to be mixed with 0.5M nitricacid. This equilibrium reaction is shown below:
{Fe(H2O)6}3+ (aq) +SCN-(aq) <-------->{Fe(H2O)5SCN}2+(aq) +H2O (l)
a) When recording the absorbance values, what should be used asa blank slution and how show its data be treated?
b) Keq is quoted to have a value of 250 at20°C. When an initial potassium thiocynateconcentration of 2x10-4M was used, the red{Fe(H2O)5SCN}2+ (aq) complex had anabsorbance value of 0.5 . If the molar absorptivity coefficient ofthe red complex is 5400 cm-1M-1 and a 1 cmcuvette was used, calculate the equilibrium concentrations of[{Fe(H20)6}3+(aq)]eq, [SCN-]eq ,[{Fe(H2O)5SCN}2+(aq)]eq
c) Briefly describe the experiment you might conduct todetermine if this reaction is endothermic or exothermic. What sortof results would lead you to conclude it was one or the other?
