Phase Diagrams

• Triple point: the temperature and pressure at which all three phases of the substance can co-exist in thermodynamic equilibrium
• Normal boiling point: temperature at which the vapour pressure is equal to
• Critical point: from this temperature point forward, no matter what pressure we apply, we cannot liquify the gas

Identify whether each of the following statements is true or false:

1. A one-component phase diagram has a single triple point where solid, liquid and vapour phases co-exist.
   • T
2. A one-component phase diagram has a single critical point above which the liquid phase does not exist.
   • T
3. A liquid will boil (i.e. the vapour pressure above the liquid equals the total pressure) at a single temperature.
   • F
4. At a given pressure, above the triple point pressure, the solid phase melts at a single temperature.
   • T
5. At a given temperature (between the triple point and the critical temperature) vapour will begin to condense to liquid at a single pressure.
   • T

Polymorphism is the existence of a solid in more than one state

Identify whether each statement is A) TRUE or B) FALSE:

1. There is a single triple point at which three phases are in equilibrium.
   • F
2. Mercury(II) iodide has a normal boiling point.
   • T
3. At temperatures below , mercury(II) iodide does not melt.
   • T
4. The vapour pressure of mercury(II) iodide at any given temperature could be determined from this phase diagram, if the axis were drawn to scale.
   • T
5. As pressure increases the sublimation temperature of mercury(II) iodide increases.
   • T