Осуществить превращения H2O--->H2--->H2S--->SO2--->H2SO3--->NA2SO3
1) 2H₂O + Ca = Ca(OH)₂ + H₂ 2) H₂ + S = H₂S 3) 2H₂S + 3O₂ = 2SO₂ + 2H₂O 4) SO₂ + H₂O = H₂SO₃ 5) H₂SO₃ + 2NaOH = Na₂SO₃ + 2H₂O
2K + 2H₂O = 2KOH + H₂ H₂ + S = H₂S 2H₂S + 3O₂ = 2SO₂ + 2H₂O SO₂ + H₂O = H₂SO₃ H₂SO₃ + 2NaOH = Na₂SO₃ + 2H₂O