1.)Na2S+H2S→2NaHS

Na+ +2S²- +2H+ +S²- →2NaHS–щелочная

2.)H2S + NH3 → NH4HS

2H+ + S²- + N- +3H+→NH4HS–кислая

3.)Cu(OH)2+H2SO4→CuSO4 +H2O

Cu²+ +2OH- +2H+ + SO4²-→Cu²+ +SO4²-+2H2O

2OH- + 2H+→2H2O–нейтральная

4.)Ba(NO3)2 + H2SO4 → BaSO4 + 2 HNO3

Ba²+ +2NO3- + 2H+ +SO4²-→BaSO4+2H+ +NO3-

Ba²+ +SO4²-→BaSO4–нейтральная среда