Barium hydroxide has a molar mass of 171.34 grams per mole. The molar mass of a chemical compound is determined by adding together the molar masses of all of the atoms present in that compound. The molar mass of each atom is found on the periodic table of elements.
The formula for barium hydroxide is Ba(OH)2, meaning one atom of barium is present along with two each of oxygen and hydrogen. Barium's molar mass is 137.33 grams per mole, while hydrogen's molar mass is 1.01 grams per mole, and oxygen has a molar mass of 16 grams per mole. Combining the molar masses of one barium atom along with two atoms each of hydrogen and oxygen yields a total molar mass of 171.34.