Applying Le Chatelier's to aqueous equilibrium questions

[Annika_Karody_3L]

On the 2013 midterm, 8A parts a and b ask about the effect of the addition lactic acid and oxygen, respectively, on the concentration of HbO2- in blood.

I got the correct answers ( increases and decreases, respectively,) but I justified it by le chatelier's, and the answer key justifies it by the interactions between the added molecules and Hb. I am wondering why this is, and if my reasoning is still justified.

Thanks!

[Chem_Mod]

This question is actually from the Fall 2013 Final Exam.

Thinking of this in terms of Le Châtelier's principle is a sound method. More specifically, you could have written about the actual chemical interactions as in the solution provided.