(a) What is the significance of the triple point in a phase diagram? (b) Could you measure the triple point of water by measuring the temperature in a vessel in which water vapor, liquid water, and ice are in equilibrium under 1 atm of air? Explain.

The triple point in a phase diagram is the point where all three phases of a substance (solid, liquid, and gas) can coexist in equilibrium, which defines the unique pressure and temperature conditions required for the simultaneous existence of these three phases. It is significant because it indicates when a substance can transition directly from one state to another without passing through intermediate states. The triple point of water occurs at approximately 0.01°C (273.16 K) and a pressure of 611.7 Pa (0.00604 atm). However, it is not possible to measure the triple point of water in the given scenario, as the air pressure inside the vessel is 1 atm, which is much higher than the required pressure. Therefore, the equilibrium of water vapor, liquid water, and ice under 1 atm of air will not take place at the triple point, and a precise measurement would not be possible.