The triple point of CO2 is above 1 atm (5.1 atm).
Following the dashed 1 atm line from low T to high T, CO2 transitions from:
- Acheck_circle
Solid directly to gas (sublimation)
- B
Liquid to gas only
- C
Gas to solid
- D
Solid to liquid to gas
Explanation
At 1 atm (below the triple-point pressure), CO2 cannot exist as a liquid; warming sublimes solid directly to gas, which is why dry ice sublimes.