What does the subscript indicate in the chemical formula #CO_2#?

1 Answer
Jan 14, 2016

Answer:

Clearly, it illustrates the physical state of the carbon dioxide: solid, gas, or (very rarely!) liquid.

Explanation:

Dry ice (aka card ice) sublimes at #-78# #""^@C#, i.e. it undergoes the transition from solid to gas. At #1# #atm# pressure, carbon dioxide does NOT exist in the liquid state, whatever the temperature.

Under exceptional circumstances, carbon dioxide can exist as a liquid: see here.