Question

Ba-->Ba(OH)2-->Ba(NO3)2-->BaSO4

Answer 1

2Ba+O2=2BaO
BaO+H2O=Ba(OH)2

Ba(OH)2+Mg(NO3)2=Ba(NO3)2+Mg(OH)2

Ba(NO3)2+K2SO4=BaSO4+2KNO3