[BrahmaBull9813]

I'm currently studying chemical equilibrium. In the textbook it says:

"The solid N2O4 vaporizes as it is warmed above its boiling point (21.2 C) and the gas turns progressively darker as the colorless N2O4 gas dissociates into brown NO2 gas."

I've never encountered the idea that a gas could have a boiling point, let alone boil. Can someone more knowledgeable please explain this idea?

Thank you
BB9813

[Borek]

I've never encountered the idea that a gas could have a boiling point, let alone boil.

Really? You have never heard about vaporization and condensation?

[BrahmaBull9813]

I've never encountered the idea that a gas could have a boiling point, let alone boil.

Really? You have never heard about vaporization and condensation?

I know that liquids vaporize into gases and gases condense into liquids, but I've never encountered the idea that a gas can boil, no. That's answering my question with a question though and that's not very... helpful.

[BrahmaBull9813]

Whoops, I misread the statement.

It said 'solid' N2O4 vaporizes. I suppose the process of sublimation/deposition occurs for this species but when it says that it 'boils', do bubbles literally form on the surface of the N2O4 solid? I always assumed that the solid simply corrodes away into a gaseous state.

[Borek]

I've never encountered the idea that a gas can boil, no.

Is boiling point property of a gas?

I have here a piece of iron, some water and some oxygen (neither in a pure form), one is solid, one is liquid, one is gaseous. When I think about them boiling I don't think about boiling point of a solid, boiling point of a liquid and boiling point of a gas, I think about boiling point of iron, boiling point of water and boiling point of oxygen.  Boiling point is not a property of a phase, it is a property of a SUBSTANCE.

That's answering my question with a question though and that's not very... helpful.

Actually it is quite helpful.

[BrahmaBull9813]

Is boiling point property of a gas?

I have here a piece of iron, some water and some oxygen (neither in a pure form), one is solid, one is liquid, one is gaseous. When I think about them boiling I don't think about boiling point of a solid, boiling point of a liquid and boiling point of a gas, I think about boiling point of iron, boiling point of water and boiling point of oxygen.  Boiling point is not a property of a phase, it is a property of a SUBSTANCE.

I don't believe that boiling point is the property of a gas. I've only learned that liquids boil, and that certain substances (eg. CO2 {s}) may sublime.

• From your example -- then, considering that the substances are in different phases, would they be characterized as (i) Iron {s} → frozen, (ii) water {l} → liquefied, and (iii) oxygen {g} → vaporized?

• Or, would (i) and (ii) be characterized as below the boiling point and (iii) above the boiling point?

• I didn't understand the statement -- "Boiling point is not a property of a phase, it is a property of a SUBSTANCE." Are you referring to the idea that different substances have different boiling points?

Actually it is quite helpful.

And I apologize. I just read that this forum is tailored to use the Socratic method to aide in the understanding of Chemistry.

I'll try to acclimatize myself to this system.

[Borek]

I didn't understand the statement -- "Boiling point is not a property of a phase, it is a property of a SUBSTANCE." Are you referring to the idea that different substances have different boiling points?

Yes. For a given substance it doesn't matter if you have it as a solid, as a liquid or a gas. There is a temperature (it depends on a pressure) that this substance will boil at, that is its boiling point. Doesn't matter if the substance is in the form of solid, liquid or gas, if it will be brought to the state where there will be boiling liquid (at 1 atm) its temperature will be always the same.