Partial pressure of oxygen dissolved in blood is 50 mm Hg. That means that: 1. It exerts a force per cm^2 equal to that of a column of mercury with 1 cm^2 base and 50 mm height
2. It would be in equilibrium with gaseous oxygen that is at partial pressure of 50 mm Hg
3. Both (1) and (2)
4. Neither (2) or (2)