Question:
Suggest a reason as to why CO is poisonous.
Solution:
Carbon monoxide is highly-poisonous because of its ability to form a complex with haemoglobin. The $\mathrm{CO}-\mathrm{Hb}$ complex is more stable than the $\mathrm{O}_{2}-\mathrm{Hb}$ complex. The former prevents $\mathrm{Hb}$ from binding with oxygen. Thus, a person dies because of suffocation on not receiving oxygen. It is found that the CO-Hb complex is about 300 times more stable than the $\mathrm{O}_{2}-\mathrm{Hb}$ complex.