Chapter 21, Problem 87AE

Carbon monoxide is toxic because it binds more strongly to iron in hemoglobin (Hb) than does O₂. Consider the following reactions and approximate standard free energy changes:

$\begin{array}{l}\text{Hb}+{\text{O}}_2\to {\text{HbO}}_2\Delta G^{\circ }=-70\text{kJ}\\ \text{Hb +CO}\to \text{HbCO}\Delta G^{\circ }=-80\text{KJ}\end{array}$

Using these data, estimate the equilibrium constant value at 25°C for the following reaction:

${\text{HbO}}_2+\text{CO}\rightleftharpoons \text{HbCO}+{\text{O}}_2$