An industrial gas scrubbing solution is maintained at a pH of $6.80$ to capture acid emissions. Hydrogen sulfite ions, ${HSO}_3^{-}$, and sulfite ions, ${SO}_3^{2-}$, act as a buffer to keep this pH stable. The $p{K}_a$ value for the acid dissociation of hydrogen sulfite is $7.18$:

$${HSO}_3^{-}(aq)\rightleftharpoons H^{+}(aq)+{SO}_3^{2-}(aq)$$

Explain, in terms of equilibrium, how this sulfite mixture acts as a buffer to control pH, and calculate the $[{SO}_3^{2-}]:[{HSO}_3^{-}]$ ratio in this scrubbing solution.

Myoglobin is an oxygen-storage protein found in muscle tissue. It contains a heme group with an ${Fe}^{2+}$ ion at its center. Explain, using the concepts of coordination and ligand substitution:

• how myoglobin binds and stores oxygen in muscles,
• why carbon monoxide poisoning severely disrupts this process.