(a) What is the significance of the triple point in a phase dia gram? (b) Could you measure the triple point of water b measuring the temperature in a vessel in which water vapo liquid water, and ice are in equilibrium under one atmospher of air? Explain.

The triple point in a phase diagram represents a unique set of conditions (temperature and pressure) at which all the three phases of a substance, i.e., solid, liquid, and gas, coexist in equilibrium. In other words, it is the point at which the substance can transform from one phase to another, and all three phases are stable at the same time.

We are now asked if we can measure the triple point of water by having water vapor, liquid water, and ice in equilibrium in a vessel under one atmosphere of air. The triple point of water occurs at a specific temperature (273.16 K) and pressure (611.657 Pa). However, one atmosphere of air is equivalent to a pressure of 101325 Pa, which is much higher than the triple point pressure for water. Thus, under one atmosphere of air, the conditions will not be the same as the triple point, and the three phases of water will not be in equilibrium. Therefore, it is not possible to measure the triple point of water by simply having the three phases under one atmosphere of air, as the pressure and temperature conditions would not align with the triple point values.