Where, n is number of moles (mol), m is mass of the compound (g) and M is the molar mass of the compound (g/mol).
Moles of Ba = 0.500 mol Molar mass of Ba = 137.327 g/mol
By applying the formula, 0.500 mol = m / (137.327 g/mol) m = 0.500 mol x 137.327 g/mol m = 68.6635 g m ≈ 68.7g Hence, the mass of Ba in 0.500 mol is 68.7 g.
