1) FeSO4 + 2NaOH = Fe(OH)2+Na2SO4
Fe"2+" + SO4"2-" + 2Na"+" + 2OH "-" = Fe(OH)2 + 2Na"+" + SO4"2-"
Fe"2+" +2 OH "-" = Fe(OH)2
2)NaOH+HNO3=NaNO3+H2O
Na++OH- +H+ +NO3-=Na+ +NO3-+H2O
H+ +OH-=H2O
3)2NaCl+H2SO4 = Na2SO4+2HCl
2Na(+1)+2Cl(-1)+2H(+1)+SO4(-2) = 2Na(+1)+SO4(-2)+2H(+1)+Cl(-1)