Solid `CO_(2)` is proved as white snow by

Options

A. expanding the gas at high temperature
B. cooling the gas below Boyel's temperature
C. expanding (adiabatically) the compressed gas from the cylinder
D. cooling the gas below its inversion temperature

Answer

C

Explanation

`CO_(2)` is usually conveyed in tank cars and cylinders in the liquid form. When the pressure is released, some of the liquid `CO_(2)` vaporizes. Adiabatic expansion causes cooling. The heat absorbed in the expansion process (overcoming the dispersion forces between molecules) is enough to cool the remaining liquid below its sublimation point `-78^(@)C` at atmospheric pressure. By inverting the cylinder and opening the valve, solid `CO_(2)` (dry ice) can be collected in a gauze bag or in a `CO_(2)` "patty maker" at room temperature.