Question

Using the phase diagram for CO₂, what phase is carbon dioxide in at -70°C and 1 atm pressure?

O A. It is in the gas phase.
O B. It is in the liquid phase.
O C. It is in the solid phase.
O D. It is at its melting point.

Answer 1

At -70°C and 1 atm pressure, carbon dioxide is in the solid phase according to its phase diagram.

Step-by-step explanation:

Using the phase diagram for CO₂, we can ascertain the phase of carbon dioxide at -70°C and 1 atm pressure. The triple point of CO₂ is at -56.6°C and 5.11 atm, indicating that below this pressure, CO₂ cannot exist as a liquid. Liquid CO₂ can only exist at pressures above 5.11 atm. At 1 atm and -70°C, which is below the normal sublimation temperature of -78.5°C, carbon dioxide will be in the solid phase. Therefore, the correct answer is C. It is in the solid phase.