The protein metmyoglobin and imidazole form a complex in solution. The molar extinction coefficient for metmyoglobin is 0.942L/mol cm at 500 nm . The molar extinction coefficient for complex is 0.688L/mol cm at 500nm Equilibrium is established in a solution which has an initial concentration of metmyglobin equal to a 0.59M. The soluton reaches equilibrium and demonstrates an absorbance of 0.435 at 500 nm.
Assuming the reaction is metmyglobin ----------> complex
What is the value of K, the equilibrium constant for the reaction?
First we have to find the concentration of complex at equilibrium:
Given that absorbance A = 0.435
lenth of cuvette l = 1cm
molar extinction coefficient for complex, e = 0.688 L/(mol.cm)
concentration of complex , c = ?
From Beer's law,
A = ecl
c = A / el
= (0.435)/ ( 0.688 L/(mol.cm) ) (1cm)
= 0.632 M
c = 0.632 M
Therefore, concentration of complex = 0.632 M
calculation of K, the equilibrium constant for the reaction:
metmyglobin ----------> complex
concentration of complex at equilibrium = 0.632 M
concentration of metmyglobin = 0.59 M
K= 0.632/0.59 =1.07
K = 1.07
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