Question

The phase diagram for a pure substance is shown above. Use this diagram and your knowledge about changes of phase to answer the following questions.

If the triple point pressure of a substance is greater than $1atm$, we expect:

• A. the solid to sublime without melting
• B. the boiling point temperature to be lower than the tripple point temperature
• C. the melting point of the solid to come at a lower temperature than the tripple point
• D. that the substance cannot exist as a liquid

Answer 1

The correct option is A the solid to sublime without melting

If the triple point pressure is greater than 1 $atm$, then the solid will not change from solid phase to liquid phase. It would instead change directly from solid to gaseous phase, as can be observed from the graph.