Respuesta :

Convert mass of BaCl2 to moles:
20.8 g BaCl2 / 208.23 = 0.100 mol
Because BaCl2 and Na2SO4 react in a 1:1 ratio, you will need 0.100 mol Na2SO4
Mass Na2SO4 = 0.100 mol X 142 g/mol = 14.2 g Na2SO4