The freons are a class of compounds containing carbon, chlorine, and fluorine. while they have many valuable uses, they have been shown to be responsible for depletion of the ozone in the upper atmosphere. in 1991, two replacement compounds for freons went into production: hfc-134a () and hcfc-124 calculate the molar masses of these two compounds.

1) HFC-134a is 1,1,1,2-tetrafluoroethane, with molecular formula C₂H₂F₄.

M(C₂H₂F₄) = 2Ar(C) + 2Ar(H) + 4Ar(F) · g/mol.

M(C₂H₂F₄) = 2 · 12 + 2 · 1.01 + 4 · 19 · g/mol.

M(C₂H₂F₄) = 102.02 g/mol; molar mass of HFC-134a.

2) 1) HCFC-124 is 1-chloro-1,2,2,2-tetrafluoroethane, with molecular formula C₂HClF₄.

M(C₂HClF₄) = 2Ar(C) + Ar(H) + Ar(Cl) + 4Ar(F) · g/mol.

M(C₂HClF₄) = 2 · 12 + 1.01 + 35.45 + 4 · 19 · g/mol.

M(C₂HClF₄) = 136.46 g/mol; molar mass of HCFC-124.