Can Henry's law be applied to find $\ce{[O2]}$ in alveoli blood?
This kind of question appeared in an another forum and I've been struggling to find a definitive answer. My initial thought was 'no', because Zumdahl's Chemical Principles book says that

Henry's law is obeyed most accurately for dilute solutions of gases that do not dissociate or react with the solvent. $\ce{O2}$ will bind to the haemoglobin in the blood. Given this reaction in the solvent, $\ce{O2_{(g)}}$ in blood does not follow Henry's law.

However, a quick google search turned up multiple sources that use Henry's law directly to find the dissolved oxygen concentration (which is about $2\%$ of total oxygen):

http://www.umich.edu/~projbnb/cvr/O2transport.pdf https://www.ncbi.nlm.nih.gov/books/NBK54103/

What I failed to understand is why the dissolved oxygen is linearly proportional to the partial pressure while the oxygen dissociation curve is not. Is there something I'm missing?


Henry's law states that the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas.

Oxygen has a larger partial pressure gradient to diffuse into the bloodstream, so it's lower solubility in blood doesn't hinder it during gas exchange. Therefore, based on the properties of Henry's law, both the partial pressure and solubility of the oxygen and carbon dioxide determine how they will behave during gas exchange.

I encourage you to read the article below.

Source: Boundless. “Henry's Law.” Boundless Anatomy and Physiology. Boundless, 21 Sep. 2016. Retrieved 16 Oct. 2016

  • $\begingroup$ Thanks, the article was very insightful but did not properly address my question. But it got me thinking that air pressure in the lungs might stay fairly constant and thus the oxygen dissociating into hemoglobin will not affect the dissolved oxygen predicted by Henry's law. Might this be a correct line of thought? $\endgroup$ – A. La Oct 16 '16 at 20:55

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