N
NaCl + BaSO4 --> Na2SO4 + BaCl2
__________________________________-----------------------------------------____________________________________
FeCl2 + NaOH -> Fe(OH)2 + NaCl
..........................................
H2O + NaCl ---------->Na2O + HCl
......................................................
$Ba(HSO_4)_2+Ba(OH)_2--->2BaSO_4+2H_2O$
.................................
Fe(OH)2--to-->FeO+H2O
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