Question

${\mathit{O}}_{\mathbf{2}}\left(g\right)$obeys Henry’s law in water but not in blood (an aqueous solution). Why?

Short answer

It does not follow Henry’s law because oxygen is associated with hemoglobin.

Step-by-step solution

Step 1: Defining Henry’s Law

Henry’s Law states that the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid.

Step 2:  Reason why Oxygen does not obeys Henry’s law in blood

The oxygen present in the blood reacts with the hemoglobin in the bloodstream. This increases the solubility of oxygen in the blood without the increase in the partial pressure of oxygen and hence henry’s law is mostly obeyed by diluted solutions of gases that doesn’t react with the solvent.