The chlorofluorocarbon CCl2F2 was once used as a refrigerant. What mass of this substance must evaporate to freeze 2 mol water initially at 20°C? (ΔHvap for CCl2F2 is 289 J/g; ΔHfus for solid ice is 6.02 kJ/mol; specific heat capacity for liquid water is 4.184 J/g•°C)