Fe(NO3)3. 9H2O in 0.5M HNO3 forms a colorless hexa-aquocomplex with the chemical formula {Fe(H2O)6}3+ (aq). This complex can...

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Chemistry

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) K_eq is quoted to have a value of 250 at20Â°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?

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3.6 Ratings (346 Votes)

Complexometric reaction a The black for the reaction would be a solution made only of FeNO339H2O and HNO3 in water This solution will not form any red complex and thus the complexed solutions with SCN would have higher absorbance which is corrected by substrating the blank See Answer

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