In a hospital, pure oxygen may be delivered at 50 psi (gauge pressure) and then mixed with N₂O. What volume of oxygen at 20°C and 50 psi (gauge pressure) should be mixed with 1.7 kg of N₂O to get a 50%/50% mixture by volume at 20°C?

(a) 0.21 m³;

(b) 0.27 m³;

(c) 1.9 m³;

(d) 100 m³.

One type of gas mixture used in anesthesiology is a 50%/50% mixture (by volume) of nitrous oxide (N₂O) and oxygen (O₂), which can be premixed and kept in a cylinder for later use. Because these two gases don’t react chemically at or below 2000 psi, at typical room temperatures they form a homogeneous single gas phase, which can be considered an ideal gas. If the temperature drops below -6°C, however, N₂O may begin to condense out of the gas phase. Then any gas removed from the cylinder will initially be nearly pure O₂; as the cylinder empties, the proportion of O₂ will decrease until the gas coming from the cylinder is nearly pure N₂O.