Baco3---BaO----Ba(oh)2----Naoh---Na2SO4----Nacl
BaCO3 = BaO + CO2
BaO + H2O = Ba(OH)2
Ba(OH)2 + Na2SO4 = 2NaOH + BaSO4
2NaOH + H2SO4 = Na2SO4 + 2H2O
Na2SO4 + CaCl2 = CaSO4 + 2NaCl