(a) What is the difference between a CFC and an HFC? (b) It is estimated that the lifetime for HFCs in the stratosphere is \(2-7\) years. Why is this number significant? (c)Why have HFCs been used to replace CFCs? (d) What is the major disadvantage of HFCs as replacements for CFCs?

(a) CFCs contain carbon, chlorine, and fluorine atoms, while HFCs contain carbon, hydrogen, and fluorine atoms. CFCs cause ozone depletion, whereas HFCs do not due to their lack of chlorine. (b) The lifetime of HFCs in the stratosphere (2-7 years) is significant because it indicates their persistence in the atmosphere. A shorter lifetime means they break down and disperse more rapidly, reducing their potential impact on the ozone layer and global warming compared to CFCs. (c) HFCs have been used to replace CFCs because they do not contribute to ozone depletion, making them a more environmentally friendly alternative in various applications such as refrigeration, air conditioning, and aerosol propellants. (d) The major disadvantage of HFCs as replacements for CFCs is that they are still potent greenhouse gases, contributing to global warming, despite not depleting the ozone layer.