On the Mass of One Molar of Barium Acetate
To understand the mass of one molar of barium acetate, one must first know its chemical formula. The chemical formula of barium acetate is $Ba (CH_3COO) _2 $.

First, calculate the relative atomic mass of each atom. The relative atomic mass of barium ($Ba $) is about 137, the relative atomic mass of carbon ($C $) is about 12, the relative atomic mass of hydrogen ($H $) is about 1, and the relative atomic mass of oxygen ($O $) is about 16.

Second, the number of atoms is calculated according to the chemical formula. In $Ba (CH_3COO) _2 $, the number of barium atoms is 1; the number of carbon atoms, because there are 2 acetates, each acetate contains 2 carbon atoms, so the total number of carbon atoms is 2 dollars × 2 = 4 $; the number of hydrogen atoms, each acetate contains 3 hydrogen atoms, a total of 2 dollars × 3 = 6 $hydrogen atoms; the number of oxygen atoms, each acetate contains 2 oxygen atoms, a total of 2 dollars × 2 = 4 $oxygen atoms.

Third, calculate the molar mass of barium acetate, that is, the molar mass. The molar mass is numerically equal to the relative molecular mass. The relative molecular mass of $Ba (CH_3COO) _2 $is: the relative atomic mass of the barium atom plus the sum of the relative atomic mass of the carbon atom, the sum of the relative atomic mass of the hydrogen atom and the relative atomic mass of the oxygen atom. That is, 137 dollars + 12 × 4 + 1 × 6 + 16 × 4 $
$= 137 + 48 + 6 + 64 $
$= 255 $.

Therefore, the mass of barium acetate in one mole is 255 grams per mole.