Final answer:
HFC-134a is the chlorine-free refrigerant among the options. It is an environmentally friendly alternative to CFCs and HCFCs because it does not contribute to ozone depletion.
Step-by-step explanation:
The question asks to identify which of the provided refrigerants is chlorine-free. Among the options, HFC-134a is the only chlorine-free refrigerant. HFCs (hydrofluorocarbons) like HFC-134a (CF3-CH2F) do not contain chlorine and are used as replacements for CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons) because they do not deplete the ozone layer. In contrast, CFC-12 (CCl2F2), HCFC-22 (CHClF2), and HCFC-124 (CF3CHCl2) all contain chlorine.
Chlorine atoms from CFCs and HCFCs can react with ozone in the upper atmosphere, leading to ozone depletion. Substances like CF3-CH2F (HFC-134a) are considered more environmentally friendly alternatives that help protect the ozone layer.