Question

Solid $C{O_2}$, gets converted into gaseous state on decreasing the
A. Pressure
B. Temperature
C. Heat
D. None of these

Answer 1

Hint: First of all, we have to know what is the solid form of $C{O_2}$. Then we will see, how does it change into its Solid form and at what temperature, pressure, and other factors. This will help us to know, on decreasing what, a solid $C{O_2}$ gets converted into gaseous form.

Complete step by step answer:
Solid $C{O_2}$​ gets converted into the gaseous state by a process called sublimation. Sublimation is a
process in which solid changes directly into gaseous state without coming into the liquid state. Thus, a solid form of carbon dioxide is called Dry Ice. It is used primarily as a cooling agent. Some of its advantages are: at lower temperature than that of water ice and not leaving any residue, other than incidental frost from moisture in the atmosphere. It is used to preserve frozen foods where mechanical
cooling is not available. Carbon dioxide is gas that gets converted into solid on high pressure. On decrease in pressure liquefied gas turns into gas. Solid carbon dioxide (dry ice) turns into gas without changing into liquid on decrease in pressure and increase of temperature. Solid $C{O_2}$ gets converted into the gaseous state by decreasing the pressure to 1 atmosphere without coming into the liquid state. At atmospheric pressure it has a temperature of approx. \[ - 79^\circ C\left( { - 110,2^\circ F} \right)\]. The solid $C{O_2}$ changes directly into its gaseous state.

Therefore, the correct answer is option (A).

Note: $C{O_2}$ does not melt at room temperature and pressure because at room temperature and atmospheric pressure, carbon dioxide is usually a gas. So, when you take solid carbon dioxide and
expose it to this temperature and pressure, it will try to return to the gas phase.