The molar mass of chlorine gas is 70.90 g/mol. One molecule of chlorine gas is formed from two chlorine atoms and has the chemical formula Cl2.
The molar mass of one chlorine atom is 35.45g/mol, as can be found in the Periodic Table of Elements. To determine the molar mass of one chlorine molecule, simply add the molar masses of the two chlorine elements, or multiply the atomic mass by two. Thus, 35.45g/mol x 2 is equal to 70.90g/mol and is the molar mass of chlorine gas. In its native state, chlorine is a gas, but it can be cooled down and turned into liquid form for storage and transportation. Once released, it goes back to its native gas state.