Дано
m(Na2SO4)=28.4 g
m(Ba(NO3)2)=54.2 g
-----------------------------
mBaSO4-?
28.4 54.2 Xg
Na2SO4+Ba(NO3)2-->2NaNO3+BaSO4↓
142 233
M(Na2SO4)=142 g/mol
M(Ba(NO3)2=261 g/mol
M(BaSO4)=233 g/mol
n(Na2SO4)=m/M=28.4/142=0.2 mol
n(Ba(NO3)2)=m/M=54.2 / 261=0.207 mol
n(Na2SO4)28.4 / 142 = X/233
X=46.6 g
ответ 46.6г