An equilibrium solution is prepared by mixing 2.750 mL of 0.001650 MSCN, 5.000 m

Question

An equilibrium solution is prepared by mixing 2.750 mL of 0.001650 MSCN, 5.000 mL 0.0001650 M Fe^3+, and 2.750 mL of 0.05000 m HNO_3, The equilibrium solution's absorbance is determined to be 0.9150. Using this absorbance value and a standard curve, you determine that the equilibrium concentration of Fe(SCN)^2+ is 0.000183 M. Prepare an ICE table for the equilibrium mixture. Include the initial concentrations, change in concentrations, and the equilibrium concentrations of Fe^3+, SCN and Fe(SCN)^2+. Using the information in your ICE table, calculate the equilibrium constant. What is the value of the equilibrium constant? 1219 897 1052 488.6 239.7

Explanation / Answer

SCN- molarity = millimoles of SCN- / total volume

= 2.750 x 0.001650 / (2.750 + 5.000 + 2.750)

= 4.32 x 10^-4 M

Fe+2 = 5 x 0.001650 / 10.5

= 7.86 x 10^-4 M

Fe+2 + SCN- --------------------------------> FeSCN+2

7.86 x 10^-4 4.32 x 10^-4 0 ---------------> initial

-0.000183 -0.000183 + -0.000183 -----------------> changed

6.0 x 10^-4 2.5 x 10^-4 1.83 x 10^-4 -------------> equilibrium

equilibrium constant

Kc = (1.83 x 10^-4) / (6.0 x 10^-4 ) ( 2.5 x 10^-4 )

Kc = 1219

answer : 1 ) 1219

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