What is the mass of 0.500 mole of ba? (watch sf’s)

n = m/M

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.