According to Le Châtelier’s Principle, when the condition of the system changes the equilibrium will shift to compensate for the changes. When temperature decrease, the pressure will also decrease and this will shift the equilibrium to the side with exothermic reaction or less molecule count.
The question is not giving the equilibrium reaction of oxygen, so I assume its
O2 + Hb = HbO2
Since the number of molecules in the right side is lower, then the number of oxygen will decrease since the reaction will shift to the right.
An atom consists of a positively charged nucleus, surrounded by one or more negatively charged particles called electrons. The positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral.
