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Thermodynamics/Co2 dry ice liquid gas equilibrium in a sealed container


QUESTION: What is the equilibrium state reached in a one litre container at room temperature when one litre of dry ice warms up in a pressure vessel? Does the dry ice all become liquid or does some form a gas? Does an equivalent mass of dry ice from one litre volume dry ice produce more or less than a litre of liquid co2? What is the gas pressure in a pressure vessel of one litre when the dry ice inside melts and stays liquid, and what is the mass of dry ice required to produce liquid co2 in a one litre pressure vessel?

ANSWER: Hi Mike,

First off, the CO2 as a liquid or solid is in a condensed state.
As a gas it is in an expanded state. Each of what we call a mol of CO2 solid or liquid will become 22.4 litres of gas at atmospheric. A mol of CO2 weighs in at 44 g = 22.4 l.

The next concept is the critical temperature/pressure point. Above a certain temperature a gas will not condense to a liquid or solid. It is too complex for me to go into here but it is well explained here

I hope this helps.
Best wishes.

---------- FOLLOW-UP ----------

QUESTION: You didn't actually answer my questions. Will some of the dry ice stay liquid if the gas is held under pressure? Does liquid co2 take up more space than dry ice at room temperature?What will the gas pressure above the liquid be?

Hi Mike,
If you put 1 litre of dry ice in a sealed pressure container and allow it to warm up.
There would be 1560g of solid gas divide by 44= 35.5 mols of gas times 22.4= 794 atmospheres of pressure. What condition the CO2 will be (g/l/s) will now depend on the temperature.AS given in the phase diagramme given here.

I hope this helps.
Best wishes


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Thermodynamics, chemistry, chemical reactions, kinetics, chemical reaction safety, dust explosion technology, static electricity. General science.


Over 40 years experience as a practicing thermochemist in industry. Head of the fire and explosion laboratory of a major European chemical company (Ciba-Geigy). Now retired.

Institute of Chemical Engineers. Royal Society of Chemistry.

Chartered Chemist, Member of the Royal Society of Chemistry (C.Chem MRSC). Msc Sheffield.

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