Carbon dioxide molecules have weaker intermolecular forces of attraction than wa
ID: 780852 • Letter: C
Question
Carbon dioxide molecules have weaker intermolecular forces of attraction than water molecules. Carbon dioxide can sublime at room condition, but not water. Both water and carbon dioxide can exist in the gas phase at 1 atmosphere at the same temperature. Organic compounds behave more like carbon dioxide in terms of sublimation. Water can be sublimed using vacuum sublimator. CO2 exists in solid, liquid and gas at -57 oC and 5.1 atm, but not water. If solid carbon dioxide and solid water are in a mixture, the two solids can be separated by sublimation.Explanation / Answer
Look at the features of carbon dioxide's phase diagram. the triple point occurs at a pressure of about 5.11 atm. So we cannot find liquid CO2 under normal conditions; only solid and vapour. To get liquid CO2, we need a pressure of at least 5.11 atm. Note also that the critical pressure occurs at a fairly low value of 72.9 atm and slightly above room temperature at 304 K. CO2 is typically transported, bought and sold under pressure in liquid form. Next time you see a tanker truck on the highway with the words Liquid CO2, you will know that the truck is not cold, it is pressurized.
Super critical CO2 is used in many industrial and food based industries such as dry-cleaning and decaffeinating coffee, where it acts as a solvent above the critical point but disappears spontaneously once the pressure is released.