Question

When does carbon-di-oxide become solid?

Answer 1

Gas to solid

1. The process due to which gas turns into a solid without passing through the liquid phase is called deposition.
2. In normal temperature and pressure, the carbon-di-oxide is gaseous in nature.
3. The gases change their state when the temperature of the gases is decreased, keeping the pressure constant.
4. Similarly, carbon-di-oxide becomes solid when the temperature of carbon-di-oxide is decreased to$-78.5^{\circ }\mathrm{C}$, keeping the pressure constant at $1\mathrm{atm}$.
5. Solid carbon-di-oxide is often used as dry ice.
6. At room temperature, the dry ice becomes gaseous carbon-di-oxide. This process is called sublimation.
7. Hence, in order to keep carbon-di-oxide in the solid phase at $1\mathrm{atm}$ pressure, the temperature must be kept at $-78.5^{\circ }\mathrm{C}$ or less.