# What's the equilibrium that results if a solid is placed in an empty container at constant temperature?

I'm confused at how to approach this question (in a chapter on phase transitions) since it is so general.

My first instinct is to say that is depends on the materials P-T diagram and the temperature, such that one would need to check in what state would the specific materiel be for $$P = 0$$ and a specific temperature. I would then conclude that the material would undergo a phase transition to that state.

But, since the question is so general, I assume the answer would be the same for all solids. Furthermore, because the follow-up question concerns the solid-gas coexistence curve.

• Even at room temperature, solid tungsten has an equilibrium partial pressure of W gas that it tries to maintain. – Jon Custer Aug 20 at 12:55
• Can you solve this simpler problem? 1 g of water is placed in a 2 cm$^3$ empty box at t 50 C. What will happen? (Hint: you will need steam tables) – Themis Aug 22 at 12:26
• @Themis I can't, I don't know what steam tables are. Based on a T-P diagram I'd say the water will stay liquid assuming atmospheric pressure. I guess that isn't correct though because water commonly evaporates at room temperature? – Amit Levy Aug 22 at 13:16
• @AmitLevy OK–forget then the problem I gave you. In your case the solid will produce enough vapor via sublimation to generate the pressure that you read from your $PT$ graph. – Themis Aug 22 at 13:44
• @Themis But since the solid is placed in an empty container (vacuum), why can't the pressure be 0? – Amit Levy Aug 23 at 9:27