Question

In its solid state, carbon dioxide is commonly called as :
A. Dry $C{O_2}$
B. Dry ice
C. Carbon black
D. Carbonic acid

Answer 1

The solid state of carbon dioxide has the same molecular formula as in gaseous state $(C{O_2})$. It is a molecular solid that is formed from gaseous $C{O_2}$ at high pressure and low temperature. It has various applications as refrigerant due to its cooling effect.

Complete answer:
The solid form of $C{O_2}$ is called dry ice. At triple point, the conversion of gaseous carbon dioxide to solid carbon dioxide takes place through sublimation. Sublimation is the direct conversion of gas to solid or vice versa without getting converted to liquid phase. $C{O_2}$ gas is compressed at high pressure and low temperature $( - {56^ \circ }C)$ to form a dense , snow like , odourless solid. It sublimes at around $- {78.5^ \circ }C$ and at atmospheric pressure without melting or leaving any residue. Hence, the name. Its temperature is lower than water and therefore used an effective coolant in many areas. The uses include preservation of food and biological samples. It can also prevent rancidity of packaged food items by displacing oxygen present in them. Wherever mechanical cooling is not possible, dry ice can be used. It can also function as a fire extinguisher due to its cooling property and ability to eliminate oxygen.
Therefore, the answer is (B) dry ice.

Note:
Dry ice should not be confused with dry $C{O_2}$ . Carbon black ,also known as lamp black and many other names is a black solid produced due to incomplete combustion of petroleum products. Carbonic acid $({H_2}C{O_3})$ is a dibasic acid formed when carbon dioxide is dissolved in water and can be used as a buffer.